Horse weight calculator: weigh your horse with a tape
This horse weight calculator estimates a horse’s body weight from two tape measurements — heart girth and body length — using the formula taught by university equine extension services. It works in inches or centimetres, gives the answer in pounds and kilograms, and has settings for mature horses and ponies, yearlings and weanlings.
Knowing your horse’s weight matters for feeding, for worming and medicine doses, and for spotting weight gain or loss before it shows. Few owners have a weighbridge, and guessing by eye is notoriously unreliable; the girth-and-length formula is much closer.
Measure with a soft plastic tape, with the horse standing square on level ground, ideally at the same time of day each time — before the morning feed is best.
How to use the Horse Weight Calculator
- Choose inches or cm and the horse’s age group.
- Measure the heart girth: run the tape round the barrel just behind the elbow and over the highest point of the withers, snug but not tight.
- Measure the body length: from the point of the shoulder straight back to the point of the buttock.
- Enter both numbers and read the estimated weight, the formula and a daily forage guide.
- Use the horse weight chart to compare other measurements at a glance.
Horse Weight Calculator features
Extension formula
Girth × girth × length ÷ 330 (inches → pounds), with 301 for yearlings and 280 for weanlings.
Inches or centimetres
The metric version uses the same formula, converted exactly (÷ 11,922 with cm and kg).
Horse weight chart
A table of weights for common girth and length combinations in your chosen unit.
Forage guide
Daily forage at 1.5–2.5% of body weight from the estimate.
Where to measure
A diagram with the girth and length lines drawn in.
The formula and a worked example
Weight (lb) = heart girth (in) × heart girth (in) × body length (in) ÷ 330. The constant 330 is for mature horses; Oregon State University Extension uses 301 for yearlings and 280 for weanlings. University of Arkansas extension gives the same 330 formula and notes it is less accurate for pregnant mares and horses with unusual conformation.
Example: girth 72 in, length 66 in. 72 × 72 × 66 = 342,144; ÷ 330 = 1,037 lb, or 470 kg. In centimetres the formula becomes girth² × length ÷ 11,922 for kilograms. Carroll and Huntington (1988), weighing several hundred horses, found almost the same constant — about 11,900.
Typical weights and feeding
Forage — hay and pasture — should make up most of the diet. University of Minnesota Extension advises feeding most mature horses at least 1% and ideally 1.5–2.5% of body weight in forage a day, so a 1,000 lb (454 kg) horse eats roughly 15–25 lb (7–11 kg) of hay a day. Pasture is mostly water, so the same weight of grass gives much less feed than hay.
Weigh or tape your horse every few weeks and keep a note. A change of 2–3 inches in girth is a real change in weight, and catching it early makes adjusting the ration easy. For other animals, see the dog weight chart.
Getting an accurate measurement
- Stand the horse square on level ground with the head in a natural position.
- Measure the girth as the horse breathes out, at the same spot each time.
- Have a helper hold the horse and another hold the far end of the tape for the length.
- Measure twice and use the average; record the date and the time of day.
Horse Weight Calculator FAQ
How do I calculate my horse’s weight?
Multiply heart girth by heart girth by body length (all in inches) and divide by 330 for a mature horse. The horse weight calculator does this for you and converts to kilograms.
Can I use centimetres?
Yes. Choose cm: the calculator uses girth² × length ÷ 11,922 and shows the weight in kilograms (and pounds).
How accurate is a horse weight tape?
A girth-only weight tape is a rough guide. Using both girth and length is more accurate — usually within a few percent for normal adult horses — but less so for pregnant mares and very fat or thin horses.
Does this work for ponies and foals?
Use 330 for mature horses and ponies, 301 for yearlings and 280 for weanlings, as Oregon State Extension recommends. Very small or very large breeds may differ more.
How much hay does a horse need?
Most mature horses need about 1.5–2.5% of their body weight in forage a day — 15–25 lb for a 1,000 lb horse.
Can I use the estimate for worming doses?
It is better than guessing, but ask your vet — under-dosing wormers encourages resistance. A weighbridge gives the most accurate weight.