There are two questions inside every large-animal evacuation, and they feel like one question because you answer them standing in the same barn aisle with the same phone in your hand.

The first is how much to load. Water, hay, buckets, medication, the tack you actually need at the far end. That question has an arithmetic answer, and the numbers behind it are published by extension services and by the National Research Council, per head, per day, by species.

The second is whether the rig can carry it. That question also looks like arithmetic. It is not, and the difference matters enough that this page keeps the two halves physically separate and gives them different levels of confidence. Every organisation that publishes the trailer weight model, without exception in what we opened, asks the person doing it to read a scale rather than to estimate. The U.S. EPA’s towing worksheet begins with a scale reading. The University of Maryland’s horse-owner fact sheet says estimating is difficult and to weigh the loaded rig. A tool that turns three horses at about a thousand pounds each into a green light against a gross combination weight rating is not a shortcut for that. It is a substitute for it, on the one output where being wrong puts a loaded trailer with animals in it onto an evacuation route.

So here is what this page is.

Instrument one is a supply calculator. Head counts, species, body weight and days in, gallons and pounds out, shown as a range across named sources rather than as a single figure, because the published figures for one horse’s daily water span roughly three to one and picking one silently would manufacture a precision nobody published.

Instrument two is a weight worksheet. Sixteen lines to fill in and ten comparisons to run, reproduced from the EPA’s own form. Some of those lines come off your door label and your owner’s manual. The rest you establish from the loaded rig, mostly at a scale, and this page tells you which is which and where the scale is.

They are not the same kind of object and they must not be merged into one number.

What This Page Deliberately Does Not Do

Four refusals, stated up front so you are not waiting for something that is not coming.

It does not print a go or no-go verdict on your rig. See above. The reason is in the sources, not in caution for its own sake.

It does not tell you how many trips you get. Our evacuation vehicle load planner has a full worked treatment of the trips question, built on a state’s own published evacuation clearance times and National Weather Service lead times, and rebuilding it here would just be a second copy that could drift out of step with the first.

It does not publish towing law. No brake threshold, no licence class, no legal load limit. Those are state vehicle code. Our two-vehicle evacuation convoy page and our rural pet evacuation with no second vehicle page both take that position already, and the rural page proves it by reading two states’ trailer brake statutes side by side to show the spread. This page holds the same line. Manufacturer ratings and federal labelling requirements are a different category from traffic law, and this page keeps them visibly apart.

It does not plan animals into a truck bed. Nothing we opened contemplates that. The bed is a supplies line, and every pound in it, plus the tongue weight of whatever you are towing, comes out of the tow vehicle’s own occupants-and-cargo allowance, which the load planner page above already covers in detail.

One more boundary, because three pages on this site now touch large animals and a reader arriving from a related-links grid sees only a title. This page is for the animals you are taking with you and the load they represent. If you are deciding when to go, horse and livestock evacuation basics owns the timing rule, and it differs by hazard. If the animals cannot be hauled at all, releasing livestock when you cannot load them works through the two published answers to that, which disagree with each other. Neither of those decisions is made on this page.

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Instrument One: The Supply Calculator

Step 1: Get the Body Weight, Because Everything Downstream Multiplies by It

Both the water figures and the feed figures below are functions of body weight. If the weight is wrong, everything is wrong, and the published finding on how wrong owner estimates run is not encouraging.

University of Tennessee Extension publication SP795 opens with it: “Estimates of a horse’s weight made by owners are often under- or overestimated by as much as 150 pounds.” On a 1,000 pound horse that is a fifteen percent error before you have multiplied by days.

SP795 states the ideal plainly: “The most accurate assessment of a horse’s weight is achieved by weighing them on a scale. Weighing on a scale is the ideal means of determining body weight in horses and other equids and should be used whenever possible.” Most owners do not have a scale, so SP795 publishes the arithmetic alternative, and it prefers two measurements over one: “Calculating body weight from measurements of the heart girth and body length tend to be more accurate than those from heart girth alone. Most “weigh tapes” available in feed stores provide a rapid estimation of body weight, but do not take into account horses with a longer or shorter body than what is considered average.”

The equation SP795 prints multiplies heart girth in inches by heart girth in inches by body length in inches, and divides that product by 330, giving body weight in pounds. Its worked example uses a heart girth of 70 inches and a body length of 78 inches and arrives at 1,158 pounds.

The scope has to travel with the equation. SP795 states it in its own words: “The calculations in the example below are meant to be used for mature, non-pregnant, light breed horses. Using this equation on draft- or warmblood-type, miniature, growing, or pregnant horses is not recommended for reliable weight estimations.” If your horse is a draft cross, a pregnant mare, a yearling or a miniature, this equation is not the tool, and SP795 says so rather than us.

How to take the two measurements, in SP795’s own sequence:

1. Stand the horse square on a flat surface.
2. Heart girth. Place a tape measure around the horse’s midsection, behind the elbow, and directly behind the highest point of the withers. Pull out the slack. SP795’s instruction is that the tape should make contact “without causing an indent in the body.” Record in inches.
3. Body length. Measure from the point of the shoulder to the point of the buttock, with the tape laying flat and making contact along the body between the two points. Record in inches.
4. Run the equation and record the result somewhere you will find it again.

SP795 adds a timing detail worth copying: horses “should be weighed on a scale or measured for weight estimation at the same time of day, preferably before morning feeding time.” Do this once on a quiet afternoon per animal, write the number on the stall card, and the supply arithmetic below takes two minutes instead of twenty.

For cattle, sheep and swine, the published water and feed figures below are keyed to weight classes rather than to a measured individual, so a class estimate is what those tables ask for. That is a difference between the horse literature and the livestock literature, not an oversight on either side.

Step 2: Water, Published as a Range and Not as a Number

This is the section where a calculator would lie to you if it picked one figure. Three publishers give five daily water figures for a horse in the table below. Their answers differ by roughly three to one, and none of them is wrong.

The horse water range, one row per issuer

Every cell below is what that source’s own page or PDF states, read on August 19, 2026. The scope column is what makes the numbers different, and it is not optional reading.

Source	Published figure	Scope the source states
Ohio State University Extension, AS-H-10-24	“50 mL/kg BW/day (0.006 gal/lb BW/day)”, worked as “6.6 gal (25 L) per day” for an 1,100 lb horse	An idle adult horse in thermoneutral conditions, and OSU prints the figure as an average; attributed by OSU to Cymbaluk, 2013. OSU adds a diet scope in the same paragraph: “Horses consuming a majority of their calories from fresh pasture will drink less water because of the high moisture content of the grass. In comparison, horses consuming mostly hay, which is dry, will drink more to meet their water needs”, attributed to Kentucky Equine Research, 2016 and Oberlin et al., 2023. An evacuated horse is on dry hay, so this row is a floor for this page’s reader rather than a planning number
Ohio State University Extension, AS-H-10-24	“1.3 gal per 100 lb of body weight (13 L per 100 kg)”	Idle horses on hot days, and OSU adds that they “will drink more when exercised”; attributed to Kentucky Equine Research, 2016
NDSU Extension, AS1763 (Revised February 2026)	8.2 gal/day at 68 degrees F; 12.7 at 86 degrees F; 11.1 at minus 4 degrees F	A mature idle horse of 1,102 lb; table adapted from NRC’s Nutrient Requirements of Horses, Sixth Revised Edition, 2007
NDSU Extension, AS1763	10.8 gal/day at 68 degrees F; 21.7 at 95 degrees F	A mature horse of 1,102 lb at moderate activity, same NRC source
UF/IFAS Extension, VM252	“at least 10–12 gallons of clean water per horse per day”	Written for equines in natural disasters, as a planning and staging figure

Two things to notice before you use any of them.

They are answering different questions. OSU’s 6.6 gallons is a physiological requirement for an idle horse in comfortable conditions. NDSU’s table adds temperature and activity as explicit variables and moves the same horse from 8.2 gallons to 21.7 gallons without changing the animal. UF/IFAS’s 10 to 12 gallons is a disaster staging figure, which is a different kind of number again: it is what to have on hand, not what the horse will necessarily drink.

The temperature dependence is the practical finding. The gap between NDSU’s 68 degree row and its 95 degree row for the same 1,102 lb horse is 10.9 gallons per horse per day. For three horses over five days that is 163 gallons, which at the USGS weight is about 1,360 pounds of difference in what you are towing, decided entirely by the weather. If the temperature and workload on your day match one of the hot rows, plan against that row rather than the mild one. We are not going to tell you how common a hot-weather haul is, because we found no publisher who counts them.

Our horse and livestock evacuation basics page already publishes the UF/IFAS figure and Purdue’s maintenance floor, and reconciles the day-count spread across AVMA, UF/IFAS, CDFA and N.C. Extension. This page is not going to restate that reconciliation; go there for how many days, and come back here for what a day weighs. How the two water figures relate is worth naming rather than leaving for you to trip over. That page stages a disaster supply against VM252’s 10 to 12 gallons, which is the right instruction when a disaster publication is the only figure in front of you, and it now also carries NDSU’s horse rows next to it, including the mature horse at moderate activity at 21.7 gallons a day at 95 degrees F, with NDSU’s own caption scope and its NRC footnote. Both numbers are correctly quoted from their own publishers, they answer different questions, and neither page blends them. If it is going to be hot and the animals are going to work, the higher figure is the one that matches your conditions. What this page adds beyond those horse rows is the other species and the arithmetic that turns gallons into towed pounds.

Do not average these, and do not weld them

It is tempting to take five figures and produce one. Do not. Averaging numbers whose scopes differ produces a further number that describes no animal in no conditions, and it would carry the borrowed authority of all three publishers while being published by none of them. If you need one number to write on a whiteboard, take the highest figure whose stated scope matches your conditions and name the source next to it.

The species this site has never published: cattle, sheep and swine

Everything above is horses. NDSU Extension publication AS1763 also tabulates the other species, and those tables are the genuinely new material on this page. AS1763 opens with the reason any of it matters: “A 10% loss of body water is fatal to most species of domestic livestock.”

The tables below are reproduced as AS1763 prints them, with its own captions and its own source footnotes in the place it puts them. Where NDSU prints no value, the cell is empty here too.

Table 1. Estimated daily water intake (gallons per head per day) for beef cows based on temperature and level of production.

Temp.	Growing 400 lb	Growing 600 lb	Growing 800 lb	Finishing 600 lb	Finishing 800 lb	Finishing 1,000 lb	Pregnant 900 lb	Pregnant 1,110 lb	Lactating 900 lb	Bulls 1,400 lb	Bulls 1,600 lb
40	4.0	5.3	6.3	6.0	7.3	8.7	6.7	6.0	11.4	8.0	8.7
50	4.3	5.8	6.8	6.5	7.9	9.4	7.2	6.5	12.6	8.6	9.4
60	5.0	6.6	7.9	7.4	9.1	10.8	8.3	7.4	14.5	9.9	10.8
70	5.8	7.8	9.2	8.7	10.7	12.6	9.7	8.7	16.9	11.7	12.6
80	6.7	8.9	10.6	10.0	12.3	14.5			17.9	13.4	14.5
90	9.5	12.7	15.0	14.3	17.4	20.6			16.2	19.0	20.6

Adapted from Nutrient Requirements of Beef Cattle: Eighth Revised Edition: Updated 2016, 2016, NRC

Three notes that belong with that table rather than after it. NDSU’s caption says “for beef cows” while the columns cover growing cattle, finishing cattle, pregnant cows, lactating cows and mature bulls; that is the caption the publication prints and we have not tidied it. NDSU prints no pregnant-cow value at 80 or 90 degrees, so neither do we, and you should not interpolate one. And the lactating column is the only one that goes down between 80 and 90 degrees, which is what NDSU prints.

Table 3. Estimated daily water intake (gallons per head per day) for horses as influenced by class, activity level and temperature.

Class	Activity Level	Body Weight (lb)	Temp. (F)	Water Intake
Yearling	Moderate	661	14	4.8
Yearling	Moderate	661	68	5.0
Pregnant		1,102	68	8.1
Lactating		1,102	68	13.5
Mature	Idle	1,102	-4	11.1
Mature	Idle	1,102	68	8.2
Mature	Idle	1,102	86	12.7
Mature	Moderate	1,102	68	10.8
Mature	Moderate	1,102	95	21.7

Adapted from Nutrient Requirements of Horses: Sixth Revised Edition, 2007, NRC

The idle mature rows are not monotonic in temperature: 11.1 gallons at minus 4 degrees, 8.2 at 68, 12.7 at 86. That is what the table prints, and NDSU’s text explains part of it by noting that “Horses fed a fiber-rich, forage-based diet require more water than those fed a more digestible grain diet.” If you are hauling in winter, the cold row is not the low row.

Table 4. Water intake (gallons per head per day) for sheep.

Class	Weight (lbs)	Water Intake
Lambs	5 to 20	0.1 to 0.3
Feeder lambs	60 to 110	1.0 to 1.5
Pregnant ewes	175 +	1.0 to 2.0
Lactating ewes	175 +	2.0 to 3.0
Rams	175 +	1.0 to 2.0

Table 5. Water requirements (gallons per head per day) for swine.

Class	Water Intake
Nursery (up to 60 lbs)	0.2 to 0.5
Grower (60-100 lbs)	0.5 to 2
Finishing (100-250 lbs.)	2 to 3
Nonpregnant gilts	3 to 5
Pregnant sows	3 to 6
Lactating sows	5 to 8
Boars	3 to 6

Table 2. Water requirements (gallons per head per day) for dairy cows based on level of production.

Class	Age	Milk Production (lbs milk/day)	Water Intake
Calves	1 to 4 months		1.3 to 3.5
Heifer	5 to 24 months		3.8 to 9.6
Milking cows	24 + months	30	18 to 22
Milking cows	24 + months	50	23 to 27
Milking cows	24 + months	80	30 to 36
Milking cows	24 + months	100	35 to 41
Dry cows	24 + months		9 to 13

There is a swine warning in AS1763 that belongs on any page about hauling animals away from their normal water supply, because the fact pattern it describes is exactly an evacuation. NDSU writes that swine on a high-energy diet “that are deprived of water (such as can occur during power outages), then are allowed free access to water (power restored), are at risk of salt poisoning (cerebral edema). They should be given access to water sparingly until fully rehydrated.” Deprived, then suddenly refilled, is what happens when a trailer arrives somewhere with a hose.

Step 3: Feed in Pounds, Which Is This Site’s Own Join

Here is a gap in the literature that a reader deserves to have named rather than papered over.

The disaster publications state feed in days. UF/IFAS VM252’s instruction is: “Obtain a 3- to 7-day supply of feed, water, and medications for all animals on the property.” Not pounds. Our horse and livestock evacuation basics page carries the full spread of day-counts across four publishers and reconciles them, which is where that question belongs.

The nutrition publications state pounds, but as a percentage of body weight, and they do not agree on the percentage. Two extension services, read the same day:

Source	Published intake	What it is measured against
Utah State University Extension, Equine Nutrition: Forages	“1.0 to 2.0 percent of its body weight daily in forage”, worked as “10-20 lbs. of cured/baled (90% dry matter) hay per day” for a 1,000 pound horse	Forage as fed, with the dry matter content stated in the same sentence
Alabama Cooperative Extension System, ANR-3153 (Revised August 2025)	“between 2 and 2.5 percent of their body weight in dry matter per day”, with the added note that “Some horses can even consume more than 3 percent of their body weight per day”; minimum “1 percent of their body weight per day”; recommended target “approximately 2 percent of a horse’s body weight per day”	Dry matter

Those are genuinely different bands, and part of the difference is that one is stated as forage as fed and the other on a dry matter basis. Utah State makes the same point from the other direction by noting what pasture does to the number: “A horse on pasture, consuming pasture at 20-30% dry matter (70-80% moisture) would require significantly more intake, approximately 30-60 lbs daily because of the extra moisture present in the pasture consumed each day.”

Alabama’s ANR-3153 also publishes the arithmetic worked out, which saves you doing it: at its 2 percent recommended rate, a 900 pound horse eats 18 pounds a day, a 1,000 pound horse 20 pounds, an 1,100 pound horse 22 pounds and a 1,200 pound horse 24 pounds. Over 30 days that is 540, 600, 660 and 720 pounds respectively, which ANR-3153 converts to 11, 12, 14 and 15 fifty-pound square bales.

Carry Alabama’s stated basis with those numbers, because it is printed in the table titles and it changes what you load. Both of ANR-3153’s tables are headed “(Dry Matter)”: “Table 1. Daily Forage and Forage Replacement Recommendations for Horses (Dry Matter)” and “Table 2. Recommended 30-Day Forage Consumption for Horses (Dry Matter)”. So every pound above is a pound of dry matter rather than a pound of hay on a scale, and ANR-3153 says what that means in its own text: “Dry matter is when moisture is removed and is approximately 10 percent for hay and 80 percent for fresh, immature pasture.” Table 2 also carries a footnote, “*Does not factor in wastage, which varies depending on feeder type.”, whose asterisk Alabama prints on the round-bale column.

The join, marked as ours, and it is narrower than it looks. Alabama Extension already does most of this multiplication: its 30-day table turns 2 percent of body weight into 540, 600, 660 and 720 pounds of forage. What no publisher we opened does is run that arithmetic over an evacuation-length day count, because the disaster publications state feed supply in days and the nutrition publications state it in percentages, and neither body of work references the other. Choosing the day count and multiplying it out is therefore this site’s own reasoning, not any publisher’s recommendation, and we are labelling it rather than dressing it in borrowed authority. If you want it in one line:

Pounds of forage to load = body weight in pounds, times the intake percentage you have chosen from the table above, times the number of days you have chosen from the sibling page’s reconciliation.

Two honest limits on that line. First, the percentages are consumption rates rather than loading recommendations, and neither Utah State nor Alabama Extension wrote them for a trailer. Second, hay wastage is real and neither figure includes it; Alabama’s own 30-day table carries the note *“Does not factor in wastage, which varies depending on feeder type.”

The things with no published weight, which you have to weigh yourself

We looked for published weights for three items and did not find them in any of the sources cited on this page.

• Hay bales. Bale weight varies with the baler, the moisture, the forage and how tightly it was tied. Alabama Extension’s own tables work in fifty-pound square bales as an assumption for conversion, not as a measurement of your hay. Put two or three of your actual bales on a scale and use your own average.
• Tack. No source we opened publishes a weight for a saddle, a set of blankets, buckets, or a muck tub. Weigh the pile you would actually load, once, on a bathroom scale.
• Water containers. A full container weighs the water plus the container, and the container is not free at large-animal volumes.

This is the same instruction our evacuation vehicle load planner gives about folding wire crates for the same reason: where the manufacturer has not published a weight, a scale in your own barn beats a number off the internet.

Step 4: Turning Gallons Into Pounds

Water is the load. USGS’s Water Science School page on water density states the measurement in plain terms: “That gallon of tap water at 70°F weighed 8.329 pounds”. Our evacuation vehicle load planner already uses that figure for household loads, so the two pages chain.

There is a second, federal statement of roughly the same thing, and it is worth reading because of what else is in the sentence. FMVSS No. 110 prescribes the text of a supplemental label for motor homes, which must state: “CAUTION: A full load of water equals XXX kg or XXX lbs of cargo @ 1 kg/L (8.3 lb/gal) and the tongue weight of a towed trailer counts as cargo”. The parallel label for recreational vehicle trailers carries the same water sentence without the tongue weight clause. That is a rule about labelling recreational vehicles rather than horse trailers, so do not read it as a requirement that applies to your rig. Read it for the two things it puts in one sentence: water is cargo, and tongue weight is cargo.

Worked example: three horses, five days

This example uses the published figures above and states which numbers are the publishers’ and which arithmetic is ours. Five days is an arbitrary illustrative figure chosen to sit inside the published spread, not a recommendation about how many days to plan for. For that, read the day-count reconciliation on our horse and livestock evacuation basics page.

Three mature horses. For the sources keyed to body weight we use 1,000 pounds; for the NDSU rows we use NDSU’s own 1,102 pound row without rescaling it, because rescaling a tabulated NRC value is not something NDSU published.

Water, five days, three horses:

Basis	Per horse per day	Three horses, five days	Weight at 8.329 lb/gal
OSU per-pound function, idle and thermoneutral (0.006 gal/lb x 1,000 lb)	6 gal	90 gal	about 750 lb
NDSU/NRC, mature idle, 1,102 lb, 68 degrees F	8.2 gal	123 gal	about 1,025 lb
UF/IFAS VM252 disaster staging figure, low end	10 gal	150 gal	about 1,250 lb
UF/IFAS VM252 disaster staging figure, high end	12 gal	180 gal	about 1,500 lb
OSU hot-day figure (1.3 gal/100 lb x 1,000 lb)	13 gal	195 gal	about 1,625 lb
NDSU/NRC, mature moderate activity, 1,102 lb, 95 degrees F	21.7 gal	325.5 gal	about 2,710 lb

The multiplication by three horses, by five days, and by 8.329 pounds is this site’s arithmetic. Four of those six rows start from a published per-head figure. Two do not: the first row and the fifth apply Ohio State’s published per-pound functions to a 1,000 pound horse, a body weight this site chose, because OSU’s own worked per-head example is 6.6 gallons for an 1,100 lb Quarter Horse rather than 6 gallons for a 1,000 lb one. The lowest per-head figure any publisher on this page states outright for an adult horse is that 6.6 gallons; NDSU’s lower rows, 4.8 and 5.0 gallons, are for a 661 lb yearling and are not a substitute for it.

One scope belongs directly under this table, from the same OSU paragraph the first row is taken from: “Horses consuming a majority of their calories from fresh pasture will drink less water because of the high moisture content of the grass. In comparison, horses consuming mostly hay, which is dry, will drink more to meet their water needs”, which OSU attributes to Kentucky Equine Research, 2016 and Oberlin et al., 2023. Step 3 of this page has you loading baled hay, so the reader of this page is provisioning the diet OSU says drinks more, and that first row is a floor rather than a plan.

Feed, five days, three 1,000 pound horses:

Basis	Per horse per day	Three horses, five days
Utah State, 1.0 percent of body weight (as fed, hay at 90 percent dry matter)	10 lb	150 lb
Utah State, 2.0 percent of body weight (as fed, hay at 90 percent dry matter)	20 lb	300 lb
Alabama Extension, 2 percent recommended target (dry matter)	20 lb	300 lb
Alabama Extension, 2.5 percent (dry matter)	25 lb	375 lb

The two 20 lb figures in that table are not the same quantity, and the basis is why. Alabama’s percentages and its 30-day table are printed on a dry matter basis: both of its tables are titled “(Dry Matter)”, and Table 2 carries the footnote *“Does not factor in wastage, which varies depending on feeder type.” Utah State’s figures are as fed, for hay it describes in the same sentence as “cured/baled (90% dry matter) hay”. Twenty pounds of dry matter is about twenty-two pounds of hay on a scale, so the pounds you actually load are the as-fed number. Converting between the two is this site’s arithmetic, not either publisher’s, and neither publisher asks you to do it.

So the supplies alone, for three horses and five days, land somewhere between roughly 900 pounds and roughly 3,085 pounds. Both ends of that band carry the feed figure on its own publisher’s basis, so the Utah State rows are already pounds of hay on a scale and the Alabama rows are pounds of dry matter, which weigh more once the moisture in real hay is counted. Add three horses at about 1,000 pounds each and you are at 3,900 to 6,085 pounds of live and consumable load, before the trailer itself, before tack, before buckets, and before a single person gets in the truck.

That spread, more than three to one on the supply half alone, is the whole argument for the next section. If the same three horses can be a 900 pound supply load or a 3,085 pound supply load depending on the weather and which publisher you followed, then no estimate you make in the barn is precise enough to be the input to a pass or fail decision about a gross combination weight rating.

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Instrument Two: The Weight Worksheet

Why This Half Is a Worksheet and Not a Calculator

Two publishers describe how to establish the weight of a loaded rig, and both of them want a scale. A third document gives you one number you can check without one, and it reaches fewer trailers than you would expect.

The U.S. EPA, in its Health and Safety Manual towing forms, defines line item 1 of its worksheet, Gross Trailer Weight, as a scale reading taken from the trailer and all its contents sitting detached from the vehicle. Line item 2, Trailer Tongue Weight, is defined this way: “Also known as Hitch Weight, this value is obtained by detaching the trailer at full load, placing only the landing gear (trailer jack) on the scale. The trailer should be at the height that it will be towed at, since the attitude affects the scale reading”. Even the axle weights are scale readings taken with only one axle on the pad.

University of Maryland Extension, writing for horse owners specifically, says: “It is important to not exceed the gross vehicle weight rating for either a vehicle or trailer, but it can be difficult to estimate the total weight of horses, people, and cargo that have been loaded into the vehicle and trailer. It is a good idea to weigh the vehicle and trailer, fully loaded, to determine the gross combination weight of the entire rig.” And then it answers the obvious follow-up question: “Weighing services are usually available at highway weigh stations or the local dump. Some grain farmers may allow use of their scales.”

Federal Motor Vehicle Safety Standard No. 110 does not tell you to weigh anything, but it does require that the trailer carry a printed cargo number, which is the one check in this whole section you can run without a scale. More on that below.

So the deliverable here is a form, a list of where each figure comes from, and ten comparisons. Fill it once on a calm weekend with the rig loaded the way you would actually load it, and keep the sheet in the truck.

EPA Table B-1: The Sixteen Lines

The EPA worksheet’s scope sentence has to travel with it every time it is cited, so here it is: “The following analysis should be conducted by an EPA staff member who has taken the Trailer Towing Safety Course. These worksheets provide a guide to ensuring that the weight distribution of the trailer is compatible with the tow vehicle and hitching system.” That is a federal agency’s internal procedure for its own trained staff, not a consumer instruction addressed to horse owners. It is on this page because it is the most complete published version of the model, and because its arithmetic is addition and comparison against published ratings rather than an invented physical model. Use it as a template; the agency wrote it for someone with training you may not have.

The worksheet also carries no printed date and no document number. Its file metadata records creation in May 2004 and modification in January 2018. We are stating that rather than implying a currency we cannot establish.

The sixteen line items, with EPA’s own names and abbreviations, and where each figure comes from:

#	Line item (EPA’s name)	Where the number comes from	Type
1	Gross Trailer Weight (GTW)	Scale, trailer and all contents, detached from the vehicle	Measured
2	Trailer Tongue Weight (TTW)	Scale, trailer at full load with only the landing gear on the pad, at towing height	Measured
3	Base Curb Weight (BCW)	EPA says this value “can usually be obtained” from the vehicle owner’s manual	Published
4	Gross Vehicle Weight (GVW)	EPA defines it as base curb weight plus all passengers and equipment, and gives a scale with the trailer detached as one way to obtain it	Measured or derived
5	Gross Combination Weight (GCW)	Scale, all wheels of loaded truck and loaded trailer, or the sum of GTW and GVW	Measured or derived
6	Gross Axle Weight - Front (GAW-Front)	Scale, front wheels only, trailer attached	Measured
7	Gross Axle Weight - Rear (GAW-Rear)	Scale, rear wheels only, trailer attached	Measured
8	Gross Vehicle Weight Rating (GVWR)	Owner’s manual, or the label inside the driver’s side door	Published
9	Gross Combination Weight Rating (GCWR)	The vehicle manual, or from the manufacturer	Published
10	Gross Axle Weight Rating - Front (GAWR-Front)	Owner’s manual, or inside the driver’s side door	Published
11	Gross Axle Weight Rating - Rear (GAWR-Rear)	Owner’s manual, or inside the driver’s side door	Published
12	Maximum Trailer Towing Rating (MTTR)	Owner’s manual, or inside the driver’s door	Published
13	Hitch Capacity (HC)	Often given on the hitch frame	Published
14	Tow Ball Rating (TBR)	Often stamped directly onto the tow ball	Published
15	Tongue Weight Rating (TWR)	Often given on the hitch frame	Published
16	Draw Bar Tongue Rating (DBTR)	Often given on the draw bar itself	Published

Six of those sixteen are figures you establish from the loaded rig rather than read off a label, and four of them can only come off a scale: gross trailer weight, tongue weight, and the two axle weights. EPA allows arithmetic for the other two. It defines gross vehicle weight as “The BCW, plus the weight of all passengers and equipment” and offers the scale as one way to obtain it, and it defines gross combination weight as either all wheels on the pad “or taking the sum of GTW and GVW”. That still leaves four numbers that decide this load shape unavailable in your kitchen, and the tongue weight is one of them.

University of Maryland Extension adds the horse-owner-specific detail on two of them. On where the trailer’s rating lives: “On a trailer, this value is listed on a tag affixed to the tongue or neck. On a tow vehicle, this value is listed on a tag inside the driver’s side door.” And on what gross combination weight rating actually covers, in words aimed at exactly this load: it “tells you the maximum that the entire rig can weigh as hauled by that particular vehicle. This value includes the weight of the vehicle itself, the trailer itself, and all cargo in the vehicle and trailer (horses, people, tack, and everything else). This value is listed in the vehicle owner’s manual.”

FS-955 also warns against reading a rating off a model rather than a vehicle: “It is also important to note that not all vehicles in the same series have the same weight rating; not every half-ton truck will have the same rating. Likewise, not every vehicle of a certain model is exactly the same. The options and variables on each individual tow vehicle will affect its gross vehicle combination weight. Always check the owner’s manual for the GCWR, and use this value as the final say in whether or not a truck-trailer combination is safe.” That is the same reason our evacuation vehicle load planner refuses to print a payload figure for any vehicle model, and this page holds the same line for tow ratings.

EPA Table B-2: The Ten Checks

With Table B-1 filled in, the EPA worksheet runs ten comparisons. Reproduced here in EPA’s own groupings, in plain language, with EPA’s own remedy column summarised in the third column.

Gross trailer weight checks

Check	Passes when	EPA’s listed remedies if it fails
GTW against MTTR	Line 1 is less than line 12	Select another tow vehicle with a higher MTTR, or reduce the GTW
GTW against HC	Line 1 is less than line 13	Select another hitch with a greater HC, or reduce the GTW
GTW against TBR	Line 1 is less than line 14	Select another hitch system or tow ball with a greater TBR, or reduce the GTW

Trailer tongue weight checks

Check	Passes when	EPA’s listed remedies if it fails
TTW as a share of GTW	Line 2 is 10 to 15 percent of line 1	Verify that the trailer is properly loaded, or select another trailer appropriate for carrying the desired load
TTW against TWR	Line 2 is less than line 15	“Decrease the TTW (keeping within 10-15% of GTW)”, or select another hitch system with a higher TWR
TTW against DBTR	Line 2 is less than line 16	“Decrease the TTW (keeping within 10-15% of GTW)”, or select another draw bar and hitch system capable of handling the load

Tow vehicle and trailer weight and distribution checks

Check	Passes when	EPA’s listed remedies if it fails
GVW against GVWR	Line 4 is less than line 8	Decrease the GVW, or select another vehicle with a greater GVWR
GCW against GCWR	Line 5 is less than line 9	Decrease the GCW, which EPA defines here as GVW plus GTW, or select another vehicle with a greater GCWR
GAW-Front against GAWR-Front	Line 6 is less than line 10	The distribution of the tow vehicle load needs to be adjusted
GAW-Rear against GAWR-Rear	Line 7 is less than line 11	“Decrease the TTW (keeping within 10-15% of GTW)”, or adjust the distribution of the trailer load

And then the rule that makes it a procedure rather than a checklist. EPA states that if any question is answered no, “efforts must be made to redistribute the load or find other equipment capable of handling the loads necessary for the specific trip”, and, critically, that if you move weight to fix one failure, “the entire analysis will have to be repeated to ensure that none of the redistributions affected other potential compatibility checklist items.” Moving four hundred pounds of water forward to fix a rear axle number changes the tongue weight, which changes two other checks. Run the whole sheet again.

EPA’s own gate on the process, in its own words: “These forms should be completed, and the inspector shall be able to answer all the checklist questions in Table B-2 with a “YES”.” And: “No trip involving the towing of a trailer can take place before both this compatibility analysis and the pre-trip inspection checklist have been satisfactorily completed.” That second sentence is an internal EPA rule binding EPA staff, not a law binding you. It is quoted here because it tells you how seriously the agency that published this model treats the difference between having filled the form in and not having filled it in.

The Rear Axle Is the Silent Failure for This Load Shape

Look at the ten checks again and notice that two of them are about axles rather than about totals. A rig can pass its gross combination weight rating and still be over its rear axle rating, and for a horse trailer that is the likely failure, not the unlikely one.

Everything heavy in this load lands behind the rear axle or on the hitch. Tongue weight, by definition, presses down at the ball, which sits behind the rear wheels. Water and hay stacked in the truck bed sit behind the rear axle. Passengers sit ahead of it. EPA’s remedy for a failed rear axle check is instructive: the first thing it lists is “Decrease the TTW (keeping within 10-15% of GTW)”, which is to say, the fix for a rear axle problem is usually a trailer loading problem.

Our evacuation vehicle load planner names the same rear-bias defect for crated animals in a car, and the mechanism is identical at a different scale. A page that checks only the combined total will pass a rig that is over its rear axle rating, so run both axle checks, not just the totals.

The One Check You Can Run Without a Scale

Many trailers carry a federally required cargo number, and where yours does, comparing your intended load against that number is a check you can run this afternoon with a tape measure and the arithmetic from Instrument One. Which trailers carry it is the first thing to settle, because the standard draws a line most readers of this page will be standing on either side of.

Section S4.3.5 of Federal Motor Vehicle Safety Standard No. 110 requires that “each trailer must on its placard contain a cargo capacity statement expressed as “The weight of cargo should never exceed XXX kilograms or XXX pounds””, and S4.3.5 goes on to place that statement in the same spot on the placard that the standard reserves for a vehicle capacity weight statement.

Now the line, in the standard’s own words. FMVSS No. 110 states its application at S2: “This standard applies to motor vehicles with a gross vehicle weight rating (GVWR) of 4,536 kilograms (10,000 pounds) or less, except for motorcycles, and to non-pneumatic spare tire assemblies for those vehicles.” The section heading says the same thing. So this check exists for a trailer rated at 10,000 pounds GVWR or less and does not reach one rated above it. We are not going to tell you which side of that line your trailer sits on, because no source we opened publishes typical GVWRs by trailer type and a guess here is the same error as a guess at a horse’s weight. What the sources do establish is that both sides of the line are populated: University of Maryland Extension FS-955 writes its licence section around the case of “towing more than 10,000 pounds”, and the Mississippi State chart reproduced further down this page runs to a maximum load of 18,400 pounds of cattle in a 34 by 7 trailer. The number that settles it for you is printed on your own trailer’s GVWR tag. S4.3.5 also excepts an incomplete vehicle, which is a manufacturing-stage term rather than anything you would buy finished. Treat a missing placard on a heavy trailer as the standard not reaching you rather than as a defect in the trailer.

If the placard is there, find it: S4.3.5 requires it to be permanently affixed near the trailer’s certification label. Then total up what you intend to put in the trailer: horses at their measured weights, hay at its weighed weight, water at gallons times 8.329 pounds, buckets, tack, bedding. That total has to come in under the printed cargo number.

Now the four things this check does not tell you, stated plainly because a single passing check is exactly the kind of thing a worried person over-reads at four in the morning:

1. It says nothing about your tow vehicle. The trailer can be inside its own cargo rating while the combination is over the truck’s gross combination weight rating. Those are separate ratings on separate labels.
2. It says nothing about the rear axle or the hitch. See the section above and the six gross-trailer-weight and tongue-weight checks in Table B-2.
3. It is not a driving rule. FMVSS No. 110 is a standard about what a manufacturer must label. What you may legally tow, with what brakes and what licence, is state vehicle code, and this page does not publish it.
4. It may not exist on your trailer at all. Above 10,000 pounds GVWR the standard does not reach the trailer, and the absence of the statement tells you nothing about whether the load is safe. If you are in that band, the scale is the whole of your answer, not a supplement to it.

Our evacuation vehicle load planner already publishes the vehicle-side placard requirement in full, including the combined-weight-of-occupants-and-cargo statement and the rule that a trailer’s tongue weight lands on the tow vehicle rather than disappearing. This page is not restating that; go there for the truck’s own budget.

Safety Margins: One Published Figure, Fourteen Years Old, and a Look-Alike That Is Not It

Neither the EPA worksheet nor FMVSS No. 110 publishes a safety margin. They publish limits and tell you to stay under them. The only margin for live weight we located anywhere is a single sentence from a single extension service:

“When hauling live weight, a good rule of thumb is to not exceed 85% of the tow vehicle’s gross combination weight rating.”

That is University of Maryland Extension Fact Sheet FS-955, dated 2012. Its reasoning runs through the paragraph above it, of which we quote three sentences: “Compatibility does not necessarily mean suitability”, and, in UMD’s own words, “Because horses (and other animals) are live cargo, special considerations should be made when evaluating weight ratings. The shifting weight of horses moving during transport can have a substantial effect on how the vehicle handles.” Note the parenthetical: UMD writes and other animals, so its reasoning is not confined to horses even though its illustration is, which matters on a page that also carries cattle, sheep and swine tables.

Publish it as what it is. It is one extension service’s stated rule of thumb, dated 2012, and it is the only published margin for live weight we located. It is not the recommended margin, because no consensus recommendation exists in the documents we opened. We were also unable to complete the currency check on it: the FS-955 PDF serves normally, but the University of Maryland’s own landing page for the publication returns a 404, so we could not check that publication index for a newer edition.

And now the look-alike. A Virginia Department of Wildlife Resources blog post from January 26, 2022, which is a reprint of a BoatU.S. Magazine article, states: “Experts suggest that the weight of the fully loaded boat/trailer be no more than 85% of the tow capacity to allow a reasonable payload in the truck.”

Same percentage. Different denominator, different cargo, different publisher. Gross combination weight rating and tow capacity are two different numbers on the same truck, and one article is about boats while the other is about horses. Presenting those two as corroborating each other would manufacture a consensus that does not exist. The same article gives a tongue weight band of “7 percent to 12 percent”, which is also not the EPA’s 10 to 15 percent, and is also for boats.

What We Could Not Read

Two gaps sit under this section and both are worth stating rather than working around.

We could not establish how a manufacturer’s published tow rating is produced. The obvious place to look is the standards body whose recommended practices the industry writes ratings against, and sae.org returned no readable content to us on August 19, 2026, either to automated retrieval or in a rendered browser session, where its own page produced only an alert and a logo. So this page names no standard and characterises none, and it has a real hole at exactly that point: we can tell you where a tow rating is printed and that it differs between individual vehicles, and we cannot tell you from a source we opened how the manufacturer arrived at it.

We could not read NHTSA’s current towing guidance. nhtsa.gov refused automated retrieval with a 403, and in a rendered browser session on August 19, 2026 the two paths we tried for a towing or trailer safety page both returned NHTSA’s own page-not-found notice, while its site search results are rendered by script and did not extract. So we do not know whether NHTSA currently publishes consumer towing guidance, and nothing on this page should be read as a claim that it does not. That is a description of two routes failing, not a finding about the agency.

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What Fits: Floor Area, Which Is a Different Question From Weight

For cattle, the binding constraint in a stock trailer is usually square footage rather than pounds, which means a weight-first tool answers the wrong question. Two organisations publish head-count charts. They are built on different column definitions and they must not be blended.

Chart one: Beef Quality Assurance

BQA’s Mature Cattle Hauling Loading Density Guidelines gives head counts for 21 trailer and compartment sizes against five cattle weights. Its column heads are point weights: 800, 1,000, 1,200, 1,400 and 1,600 pounds, with a square-feet-per-animal row above the counts reading 10.4, 13, 15.6, 18.2 and 20.8 square feet respectively, all labelled for polled cattle.

Its stated basis is printed beneath the chart in a single line, which carries a superscript footnote marker in the middle of it. Reproduced in two pieces so that the marker is not silently swallowed: “Calculations were based on FASS Guidelines”, superscript 1, “for square foot per 100 lbs. of animal needed: mature/fed cattle = 1.3 ft2”. That superscript resolves, in BQA’s own footnote, to the Federation of Animal Science Societies’ 2020 Guide for the care and use of agricultural animals in research and teaching.

The three conditions BQA prints directly under that basis line, reproduced here in the same place the source puts them:

• “For horned cattle, increase ft2 per animal by 5%.”
• “Total weight should not exceed capacity of truck or trailer and or legal load requirements.”
• “Shape of cattle and frame score factor into how cattle fit into compartment.”

And the footnote on the chart itself: *“Not all trailer sizes are included in the chart.”

A sample of BQA’s counts, so you can see how the area constraint behaves. These are BQA’s own figures for polled cattle:

Trailer/compartment size	Square feet	800 lb	1,000 lb	1,200 lb	1,400 lb	1,600 lb
16 ft x 6 ft	96	9	7	6	5	4
20 ft x 6 ft	120	11	9	7	6	5
24 ft x 6 ft	144	13	11	9	7	6
20 ft x 7 ft	140	13	10	9	7	6
24 ft x 7 ft	168	16	13	10	9	8
24 ft x 8 ft	192	18	14	12	10	9

Notice that a 24 by 6 trailer and a 20 by 7 trailer hold almost the same number of cattle despite being different shapes, because 144 and 140 square feet are almost the same area. That is what an area model looks like, and it is not what a weight model looks like.

Chart two: Mississippi State University Extension P2797

P2797, posted in 2025, publishes its own table for 19 trailer sizes, and it is built differently in three ways that matter.

First, its column heads read “Average cattle weight under, lb” and run from 400 to 1,700 pounds, which is a set of upper bounds rather than a set of point weights. Second, it carries a final column headed Max, in pounds, that BQA’s chart does not have, running from 6,500 for a 14 by 6 trailer to 18,400 for a 34 by 7. Third, MSU introduces it as “the maximum recommended numbers of polled or dehorned cattle for trailers of different dimensions”, and adds the observation that “Fewer mature or fat cattle than feeder cattle will fit on a given trailer due to the differences in cattle size and weight.”

A sample of MSU’s own figures:

Length x Width	600 lb	800 lb	1,000 lb	1,200 lb	1,400 lb	Max
16 x 6	12	9	7	6	6	7,400
20 x 6	15	12	9	8	7	9,300
24 x 6	18	14	11	9	9	11,100
20 x 7	18	13	11	9	8	10,800
24 x 7	22	16	13	11	10	13,000
32 x 7	29	22	17	14	13	17,300

A disclosure about that Max column. MSU prints its header with an asterisk, and we could not locate the footnote that asterisk points to anywhere in the publication, in the extracted text or on the rendered page carrying the table. So we are reproducing the column and saying plainly that we do not know what the asterisk qualifies. Do not assume it means the same thing as BQA’s asterisk, which is a footnote about which trailer sizes are included.

The instructions MSU prints around that table, which belong with it:

• “Do not exceed the Gross Vehicle Weight Rating for the truck and trailer. Strictly adhere to safe load levels with regard to animal weight and space allocation.”
• “Reduce trailer stocking density by 5 percent for cattle with horns. Also be sure to reduce the number of head loaded during hot conditions.”
• From the fitness-to-load passage printed on the same page as the table, in P2797’s Loading, Transit, and Unloading section: “Unless absolutely necessary, do not haul female cattle that are in the late stages of pregnancy. This will reduce the risk of calving on the trailer or stress-induced premature calving.” Note the hedge MSU itself writes in, because an evacuation is exactly the situation where absolutely necessary becomes a live question, and MSU does not answer it for you.
• “It is the driver’s responsibility to know trailer dimensions, load only the size of cattle that will safely and humanely fit the trailer, and adhere to the maximum legal load limit for the states in which they are operating.”
• “Provide adequate space for cattle to stand with little risk of being forced down because of overcrowding. When the vehicle is not full, safely partition cattle into smaller areas to provide stability for the cattle and the vehicle.”

The hot-conditions reduction is the qualifier most likely to be dropped and most likely to matter, because a summer wildfire evacuation is exactly a hot-conditions haul. It belongs to MSU alone. MSU repeats it in its own transportation conditions section: “Put fewer cattle on trailers during extreme heat conditions.” BQA’s chart carries no heat instruction at all: the words heat, hot, weather and temperature do not appear anywhere in that document, which is worth knowing if BQA is the chart you are working from. And MSU publishes no percentage for the heat reduction the way it does for horns, so this page is not going to invent one.

Why the two charts are not interchangeable

Read the column heads again. BQA’s 1,000 pound column is for cattle weighing about 1,000 pounds. MSU’s 1,000 pound column is for cattle whose average weight is under 1,000 pounds. Those are not the same set of animals, and a row taken from one chart and applied to the other is a fabricated table even though every individual number in it was published somewhere.

Use one chart, in its own terms, and say which one you used.

Horses: what we did not find

We looked for a horse equivalent of these floor-area charts in the sources cited on this page and did not find one. University of Maryland’s trailering fact sheet FS-932 discusses trailer types, partial and full partitions and the reasons to use each, without publishing a square-footage figure. UF/IFAS VM252 contains no weight, capacity or square-footage guidance of any kind; we searched its full page text on August 19, 2026 for weight, capacity, GVWR, tow and square feet and found nothing. The EPA worksheet is species-agnostic and is about weights, not areas.

That is a statement about what we opened, not a finding that no such chart exists. Horse trailer manufacturers publish stall dimensions for their own models, and that is the number to work from for your specific trailer. What FS-932 does give you is the design consideration behind the dimension: “Partial partitions give more room for the horse to spread its feet and balance itself while traveling.”

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The Haul-Interval Card

Everything above happens before you pull out of the driveway. This is the part that happens after, and it is where three publications converge on a rhythm and disagree on the interval.

The intervals, one row per issuer

Source	Interval published	What the interval is for
Ohio State University Extension, AS-H-10-24	“stopping every 3 to 6 hours to offer fresh clean water is recommended”	Offering water in transit; OSU attributes the recommendation to Houpt and Wickens, 2014
University of Maryland Extension, FS-932	Rest “approximately every 3-4 hours”	Rest for the horse; FS-932 notes fueling the vehicle is an adequate rest period
University of Maryland Extension, FS-932	“Water should be offered every 3-4 hours”	Offering water in transit
University of Maryland Extension, FS-932	Beyond 18 hours, unload and stable overnight	The outer limit of a continuous haul
Mississippi State University Extension, P2797	“Check cattle on a long haul after two hours on the road and then every four hours after that”	Checking cattle, not watering them

The two horse publications differ: three to six hours from Ohio State, three to four from Maryland. Plan to the shorter interval and you satisfy both. Note also that Ohio State’s figure is a recommendation it is passing along with an attribution to Houpt and Wickens, 2014, rather than a finding of its own, and this page is citing Ohio State as the publisher of the recommendation rather than chasing the underlying reference.

Six things the same sources add, which are easy to miss

A stopped trailer is a drinking trailer. Ohio State reports that “Even when horses may be offered water en route, they may become dehydrated; intake rates of both water and feed are greater when the trailer is not in motion (Kusunose and Torikai, 1996).” If you offer water without actually stopping, you have not really offered it.

Bring your own buckets. FS-932: “Take buckets from home so the horse can eat and drink out of familiar containers. This also reduces disease transfer from other horses.” In an evacuation, where you may be sharing a fairground water point with animals from twenty other properties, that second sentence is doing as much work as the first.

Offer it anyway. FS-932: “Some horses will not drink while traveling but should still be offered water. A few gulps of water can help avoid colic or impaction troubles during the trip.”

A hot horse gets water differently. NDSU AS1763 states that horses hot from exercise “should have steady, but controlled access to water (up to 1-2 liters every 20 minutes) to prevent colic, laminitis and/or exertional rhabdomyolysis (tying up).” Loading a panicking horse in the smoke and heat is exertion.

Hauling cattle in heat changes the rhythm, in the opposite direction. Everything above is written for horses. Mississippi State’s transportation conditions section tells cattle haulers: “Avoid transporting cattle in extreme heat conditions when possible, particularly during the hottest part of the day, which typically occurs between 11 a.m. and 4 p.m. If cattle must be hauled during these conditions, avoid unnecessary stops, and deliver cattle to their destination as quickly and safely as possible. Make stops as short as possible, stop only during cooler parts of the day, and select shaded areas for stops. Put fewer cattle on trailers during extreme heat conditions. Handle cattle especially gently and patiently during these conditions.” So a hot-weather cattle haul is not a horse haul with cattle in it. The horse publications above want you stopping every three to six hours to offer water; MSU wants the stops short, shaded, few and out of the middle of the day. If you are moving both species in one convoy, those instructions pull against each other, and neither publisher addresses the other. This page is not going to resolve that for you; it is naming it so you decide it before you are standing at a rest area.

And the cold half of the same section, which this page has to carry because it publishes winter water figures above. Mississippi State’s transportation conditions section is two paragraphs, and the second one is this: “Extreme cold and windy conditions exist when the wind chill index is below 0°F. These extreme conditions can have drastic adverse effects on cattle health and can dramatically increase cattle maintenance energy requirements. If cattle are wet, the danger is even greater. Unprotected cattle hauled at highway speeds can be subject to dangerous wind chill. If cattle must be transported during these conditions, avoid unnecessary stops, and deliver cattle to their destination as quickly and safely as possible. Do not haul cattle during icy conditions.” That last sentence carries no hedge, unlike MSU’s own late-pregnancy instruction reproduced further up this page, which begins “Unless absolutely necessary”. It is also written for cattle, and we are not extending it to horses. We audited eight of this page’s other animal publications for a cold or icy-conditions limit on hauling and found none: the words icy and wind chill appear nowhere in FS-932, FS-955, AS-H-10-24, VM252, SP795, AS1763, the BQA loading density chart or the WALARM factsheet. We did not audit the two forage publications, which are about what a horse eats rather than about transport, or the FASS guide, which this page cites through BQA’s footnote and never opened. FS-932’s transport section runs to rest, water, brakes and the 18-hour threshold and stops there, and Ohio State’s cold-weather section is about keeping water unfrozen at home rather than about the road. If you are hauling livestock in winter, that paragraph is the guidance this page has and the horse sources are silent.

Water temperature affects how much they drink. Ohio State reports that “AAEP recommends offering water between 45 to 65oF to encourage optimal water consumption”, citing a study in which consumption increased when water in that range was the only source offered compared with water at 38 degrees F or below. That is worth knowing if your staged water has been sitting in a cold trailer or in the sun.

The brake check that belongs to every stop where animals move

This one is not about water and it is the most consequential item in this section. FS-932: “Any time the load weight is adjusted during the trip (unloading or loading horses), drive a short distance and check operation of brakes before traveling onto high traffic roadways. Make adjustments to the brake controller as needed. When adjusted correctly, the trailer should not push against the towing vehicle while braking.”

In an evacuation you may well drop two animals at one destination and carry two more onward. The load that your brake controller was set for is not the load you now have.

FS-932 adds one more habit for every stop: “Any time while traveling that the driver exits the vehicle, walk around the trailer checking tires, lights and that the hitch is secure.”

What the drive itself does to your timing

If you are moving animals on foot rather than by trailer, or moving them to a loading point across a property, the practical speeds are not the speeds you are used to. The Western Area Livestock and Agriculture Risk Mitigation Project, a University of Wyoming Extension publication produced with Colorado State and Montana State Extension under a USDA NIFA grant, states it directly: “Cattle which could normally be moved 15 miles may only move 2 miles in smoke or one mile in water.” It also observes that “Various species herd and load at different paces, especially during disasters.”

That document carries a scope that must travel with it: it is written for emergency managers and organised producer teams operating inside the Incident Command System, not for one owner at a gate. Its hauling considerations list is framed the same way, asking what vehicles are available and “how many animals can be moved per trip”, whether access conditions allow those vehicles, whether relief drivers, vehicles, fuel and supplies exist for more than one operational period, and “Where do you safely stage?” One item on that list is reproduced here rather than quietly dropped, because dropping it would tidy the source: WALARM also asks “How do get authority for overloading and running more than normal hours?” That question exists because the document is written for teams operating under an incident commander who can grant such things. It is not an invitation to an individual owner to exceed a rating, and nothing else on this page should be read that way. Those questions are useful for a person planning alone too, which is why they are here, but the answers the document expects come from a team.

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The Questions This Page Refuses to Answer

Licence class and the commercial trap

University of Maryland Extension FS-955 states that most drivers hold a non-commercial class C licence, and it gives the reassuring half first: “This license is sufficient for most two- and three-horse trailers pulled by an SUV or pickup truck for non-commercial purposes.” It then sets the thresholds, stating that such a licence “permits the operation of a vehicle with a gross vehicle weight rating (GVWR) of 26,000 pounds or less and the towing of a vehicle or trailer with GVWR of 10,000 pounds or less. If you are operating a vehicle with gross vehicle weight rating (GVWR) greater than 26,000 pounds, or if you are towing more than 10,000 pounds, you will need a different class license.”

And then the sentence that catches the neighbour with the four-horse gooseneck: “Note that additional regulations apply to commercial businesses. (Per federal definition, your enterprise is considered a commercial business if any money changes hands, even if your business does not turn a profit.)” FS-955 routes that question to the Truck and Bus Enforcement Section of the reader’s state police rather than answering it.

In federal motor carrier regulation, gross combination weight rating is defined as “the greater of: (1) A value specified by the manufacturer of the power unit, if such value is displayed on the Federal Motor Vehicle Safety Standard (FMVSS) certification label required by the National Highway Traffic Safety Administration; or (2) The sum of the gross vehicle weight ratings (GVWRs) or the gross vehicle weights (GVWs) of the power unit and the towed unit(s), or any combination thereof, that produces the highest value.” The definition does not stop there, and the sentence that follows it is part of the same definition: “Exception: The GCWR of the power unit will not be used to define a commercial motor vehicle when the power unit is not towing another vehicle.” The same section defines a commercial motor vehicle in interstate commerce to include one that “Has a gross vehicle weight rating or gross combination weight rating, or gross vehicle weight or gross combination weight, of 4,536 kg (10,001 pounds) or more, whichever is greater”.

Which section number to write down, because the obvious one is not operative. These definitions are usually cited to 49 CFR 390.5, and that is the citation you will see everywhere. The Cornell Legal Information Institute mirror of section 390.5 carries an Effective Date Note recording that the section was suspended effective January 14, 2017, and that after a run of lifts, amendments and re-suspensions it was “again suspended indefinitely, effective July 21, 2026”, at 91 FR 45661. The text that is actually in force sits at 49 CFR 390.5T, which is where the quotations above are taken from. We are stating that rather than citing a suspended section as though it were live. If you take this question to your state police, take both section numbers with you.

Read that definition for what it is. It exists to decide what counts as a commercial motor vehicle in interstate commerce for the purposes of the federal motor carrier rules. It is not a rule addressed to a private owner hauling their own horses to a fairground twelve miles away, and this page is not presenting it as one. It is here because it is where the term gross combination weight rating is defined in federal regulation, and because 10,001 pounds is a lower threshold than the phrase commercial motor vehicle suggests: the Mississippi State chart reproduced above runs to a maximum load of 18,400 pounds of cattle in one trailer, before the trailer itself or the truck is counted.

The evacuation-specific version of the question, which is the reason this section exists: someone with a bigger trailer offers to take your two horses, and you offer them a hundred dollars for fuel. That is the fact pattern where an owner moving their own animals becomes something else in the eyes of a regulator. Ask your state before a season, not at the gate.

Why this page publishes no towing law

Because it varies by state, and because two live pages on this site have already done the work to prove that it varies. Our rural pet evacuation with no second vehicle page reads California’s and Florida’s trailer brake statutes side by side and shows they catch different trailers at the same nominal weight. Our two-vehicle evacuation convoy page states its refusal in as many words and routes readers to their own state’s vehicle code and DMV.

Manufacturer ratings are a different category. A gross combination weight rating is a number the manufacturer assigns to a specific vehicle, and exceeding it is an engineering problem regardless of jurisdiction. A brake threshold is a legal line drawn by a legislature, and it moves when you cross a state line. This page publishes the first kind and not the second, and the distinction is deliberate.

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Your Load Worksheet

Do the first half on a quiet afternoon. Do the second half at a scale, once, and keep the sheet in the truck.

Before anything else

• Measure and record every animal’s body weight, on a scale if you have access to one. For mature, non-pregnant, light breed horses, University of Tennessee’s SP795 equation using heart girth and body length is the published alternative; it is explicitly not recommended for draft or warmblood types, miniatures, growing horses or pregnant mares. Write the number on the stall card.
• Weigh your actual hay. Put two or three of your own bales on a scale and use your own average, because no source we opened publishes a standard bale weight.
• Weigh the tack pile you would actually load, once, on a bathroom scale.
• Copy every rating onto one sheet: the trailer’s cargo capacity placard if it has one, which federal law requires only at 10,000 pounds GVWR or less, the trailer’s GVWR tag on the tongue or neck, the tow vehicle’s door label GVWR and axle ratings, the owner’s manual GCWR and maximum trailer towing rating, the hitch frame’s capacity and tongue weight rating, the tow ball stamp, and the draw bar stamp.

The supply side

• Choose your day count from the reconciliation on our horse and livestock evacuation basics page rather than from a single publisher.
• Choose your water figure by matching the scope, not by averaging. If it will be hot, use a hot-weather figure and name which one.
• Multiply out water for every species you are moving, using NDSU AS1763’s tables for cattle, sheep, swine and dairy, which are reproduced above.
• Convert gallons to pounds at the USGS figure of 8.329 pounds per gallon at 70 degrees F. This is usually the largest single line on the sheet.
• Multiply out forage using the intake percentage you have chosen, and add a margin for wastage, which none of the published percentages include.
• Add medication, buckets, bedding and the water containers themselves. A full container weighs its water plus itself.

The weight side, at a scale

• Load the rig the way you would actually load it, including people, and go to a scale. University of Maryland points to highway weigh stations, the local dump, and, with permission, grain farmers’ scales.
• Before that first fully loaded drive, go a short distance, check the brakes and adjust the brake controller. This trip to the scale is the first time the rig has ever carried this load, and this page has just argued you do not yet know whether it is inside its ratings. FS-932 gives that brake instruction for load changes made during a trip, quoted under On the road below. Applying it to the first loading is this page’s own reasoning rather than FS-932’s instruction, and the reason is the same one FS-932 gives: the controller setting that suited an empty or lightly loaded trailer is not the setting for a loaded one.
• Take the four unavoidable scale readings in EPA’s Table B-1: gross trailer weight detached, tongue weight with only the jack on the pad at towing height, and the front and rear axle weights with the trailer attached. While you are on the pad, take gross vehicle weight with the trailer detached and gross combination weight with everything on it as well, since EPA lets you reach those two by arithmetic instead and you may as well have both routes to compare.
• Run all ten comparisons, not just the total against the gross combination weight rating. The two axle checks and the six gross-trailer-weight and tongue-weight checks are where this load shape actually fails.
• If any comparison fails, fix it and then start the whole analysis again, because EPA states that a redistribution to fix one item can break another.
• Run the no-scale check too, if your trailer is rated at 10,000 pounds GVWR or less: horses plus feed plus water plus tack against the trailer’s own printed cargo capacity number. Above that rating the standard does not reach your trailer and the statement may not be there. Remember that passing it says nothing about the truck, the axles or the hitch.
• Note where you land against 85 percent of your gross combination weight rating, which is University of Maryland Extension’s 2012 rule of thumb for live weight and the only published margin we located. It is one extension service’s rule of thumb, not a consensus, and it is not the same 85 percent that a boating article measures against tow capacity.

If you never weighed and you are leaving tonight

This section is this site’s own reasoning, not any publisher’s, and it exists because the rest of this page is written for a calm weekend and evacuations are not. Here is what is honestly available to a household loading tonight that has never seen a scale reading, and what is not.

• If your trailer is rated at 10,000 pounds GVWR or less, the FMVSS No. 110 cargo capacity placard is the one check you can run in the barn, and it is a real one. Total the horses at their measured weights, the hay at its weighed weight, the water at gallons times 8.329 pounds, plus buckets, tack and bedding, and compare that total against the printed number. Passing it says the trailer is inside its own cargo rating. It says nothing about your tow vehicle’s gross combination weight rating, nothing about either axle, and nothing about the hitch, tow ball or draw bar, because those are separate ratings compared against weights you do not have.
• If your trailer is rated above 10,000 pounds GVWR, the standard does not reach it, the placard may not exist, and no check is available to you without a scale. That is the honest answer and it is the same one the section above gives. Reduce what you can reduce, which is the consumable load: water is the heaviest thing on the sheet and the least fixed, so a shorter first leg to a place you can refill is the one lever that is entirely yours.
• Either way, the number of trips is a different question and this page does not own it. Our evacuation vehicle load planner works it through against published clearance times and lead times.
• Then weigh it afterward. The first calm weekend after you get home is the point of the worksheet above, and the numbers do not expire.

On the road

• Horses: plan a stop at least every three to four hours to rest and offer water, which satisfies both the Ohio State and the Maryland intervals.
• Cattle in heat: the opposite rhythm. Mississippi State P2797 tells cattle haulers to avoid unnecessary stops, to make stops as short as possible, to stop only during cooler parts of the day and in shaded areas, and separately to check cattle on a long haul after two hours on the road and then every four hours after that, which is a checking interval and not a watering one. If you are moving both species in one load, see the haul-interval card above; neither publisher addresses the other and this page does not resolve it.
• Cattle in extreme cold or ice: Mississippi State draws a harder line still. P2797 puts extreme cold and windy conditions at a wind chill index below 0 degrees F, tells haulers in those conditions to avoid unnecessary stops and deliver as quickly and safely as possible, and states flatly: “Do not haul cattle during icy conditions.”
• Horses: actually stop. Intake is higher when the trailer is not moving.
• Carry your own buckets from home.
• After any stop where animals come off or go on, drive a short distance and check the brakes before rejoining a high-traffic road, and adjust the brake controller.
• Walk the trailer every time you get out: tires, lights, hitch.
• If the haul will run past 18 hours, arrange overnight stabling in advance, per FS-932, rather than pressing on.
• Get a veterinarian involved for any animal that will not drink, that arrives distressed, or that was hot and hard-loaded before departure. This page publishes no treatment, no dosing and no home management, and none of the arithmetic above is a substitute for someone looking at the animal.

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How We Sourced This, and What We Refused to Publish

Every figure on this page was read from the publisher’s own PDF or page on August 19, 2026, and confirmed by content rather than by URL. Three of those confirmations are worth naming because they would each have produced a wrong page.

A URL that disagrees with its own document. NDSU’s livestock water publication serves from a file named as1783.pdf, and the document’s own header reads AS1763, Revised February 2026. We are citing it as AS1763 because that is what the document says it is, and we are disclosing the mismatch rather than quietly picking one.

A PDF that drops letters in extraction. The WALARM livestock evacuation factsheet loses its tt and ti ligatures when its text is extracted, so the word Cattle comes out of the extractor with its double t missing and evacuation comes out with its ti missing. We confirmed the sentence we quote against a rendered image of the page rather than trusting the extraction, because quoting an extraction artifact would have put characters inside quotation marks that the document does not contain.

A table column with an asterisk and no footnote. Mississippi State’s P2797 heads its final column Max with an asterisk. We searched the publication for the footnote and did not find it, so we reproduce the column and say we do not know what the asterisk qualifies, rather than inventing a plausible meaning for it.

What we refused to publish.

A single number for how much water a horse needs. Three publishers give five figures spanning roughly three to one for the same animal, and they are answering different questions. Averaging them would produce a number nobody published, carrying the authority of three organisations, describing no horse.

A pass or fail verdict on any rig. This is the central refusal and it is the one the slug on this page most invites. EPA’s model runs on scale readings. Maryland’s fact sheet says estimating is difficult and to weigh the loaded rig. A tool that converted head counts and nominal weights into a green light would substitute an estimate for the measurement all of them require, and it would do it on the single output where being wrong loads an over-weight trailer with animals in it onto a road that is already failing.

A tow rating, payload figure or trailer weight for any specific model. Our vehicle load planner page refuses to print payload figures for the same reason, and University of Maryland Extension states the reason in its own words: not every half-ton truck has the same rating, and the owner’s manual for the individual vehicle is the final say.

A merged cattle chart. BQA’s columns are point weights and Mississippi State’s are upper bounds. Both charts appear above, separately, in their own terms, with their own footnotes, because a row from one applied to the other would be a fabricated table made entirely of published numbers.

Mississippi State’s cold-weather cattle rules restated as horse rules. P2797 puts extreme cold at a wind chill index below 0 degrees F and says flatly not to haul cattle during icy conditions. That paragraph is reproduced above where it belongs, in the section on hauling cattle. We audited eight of the other animal publications cited here for a cold or icy-conditions limit on hauling and found none, naming every one of them where that paragraph is reproduced, so we have not manufactured one by extension, and a reader hauling horses in winter should know that the silence is the sources’ and not ours.

A percentage for the hot-weather stocking reduction. Mississippi State tells you twice to load fewer head in heat and publishes no figure for it, so neither do we. BQA prints a horned-cattle adjustment and no heat instruction at all, so we have not credited it with one.

A weight for a hay bale, a saddle or a water tub. Nobody we opened publishes one, they vary enormously, and the honest instruction is a bathroom scale.

Any towing law, licence rule or legal load limit. State vehicle code, and our own siblings have already demonstrated that it differs between states at the same nominal weight.

Anything clinical. This site has no credentialed veterinary reviewer. The water intakes, the dehydration signs and the post-exertion watering rule above are quoted from extension publications because they bear on how much to load and when to stop. Deciding whether a particular animal is fit to travel, or what to do about one that is not, is a veterinarian’s call, and the page says so at every point where a reader might reasonably want more.

We did not test any product, weigh any trailer, or drive any evacuation route. Full methodology at /review-methodology.

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Where to Go Next

This page is the load-and-supply spoke of our pet emergency playbooks hub, and it covers one narrow thing: what a large-animal evacuation load weighs, and how to establish whether your rig can carry it.

If you are deciding when to go. Horse and livestock evacuation basics owns the timing rule, and it is different in fire country than on the hurricane coast. It also owns the day-count reconciliation this page keeps pointing at, the trailer readiness inspection list, the identification layers, and the shelter-in-place branches.

If you do not yet know where the trailer is going. Finding a large animal evacuation center covers the destination and what it will ask you for on intake. This page sizes what the rig has to carry to get there; that page sizes what the destination expects once you arrive.

If the animals cannot be hauled at all. Releasing livestock when you cannot load them works through a decision on which published authorities disagree with each other, and it is not a decision this page makes.

If you have no trailer or no second driver. Rural pet evacuation with no second vehicle covers borrowed transport, four jurisdictions’ large-animal programmes in their own words, and the trailer brake statutes of two states read side by side.

If the load is crates and carriers rather than horses. Evacuation vehicle load planner covers the tow vehicle’s own occupants-and-cargo placard, roof boxes and hitch carriers, the loading order, and how many trips you actually get.

If two vehicles are going. Two-vehicle evacuation convoy covers splitting animals across vehicles and the pre-departure checks that belong to both.

Then do the one thing that pays off most. Take the truck and the empty trailer to a scale this month and weigh them, then weigh them again loaded before the season starts. Two numbers, one afternoon, and the difference between running a worksheet and guessing at the gate.