Horse Weight Calculator
Enter the heart girth and body length of a horse. The calculator estimates its weight in pounds and kilograms with the formula that many weight tapes use.
How to use this Horse Weight Calculator
- Choose inches or centimeters.
- Measure the heart girth with a soft tape, just behind the elbow, over the withers, with the horse standing square.
- Measure the body length from the point of the shoulder to the point of the buttock.
- Enter both numbers.
- Press Calculate. Repeat a few times and take an average.
How to estimate horse weight
The common formula uses the heart girth squared times the body length.
- Weight (lb) = girth in inches squared x length in inches / 330
- Weight (kg) = pounds / 2.2046
Worked example
A horse has a heart girth of 72 inches and a body length of 66 inches. The weight is 72 x 72 x 66 / 330 = 1,037 lb, or 470 kg.
Measure at the same time of day, because gut fill and water change the result. Take each measurement two or three times and use the average, since a small error in girth has a large effect when it is squared. The formula is made for adult horses of average build. It may be less accurate for ponies, foals, draft horses, pregnant mares and horses that are very thin or very fat. If a horse gets medicine or a dewormer that is dosed by weight, a scale or a vet check is a better way to find the weight than an estimate from a tape. Keep a record of the weight and the date each time you measure, so that you can see whether your horse is gaining or losing over the seasons. A change of more than a few percent over a short time is worth a talk with your vet. A weight tape or a body condition score can be used on the same day, and the two together give a better picture than either alone. Feed amounts for hay and grain are often set as a share of body weight, so a good estimate also helps you plan your feed and your budget through the year.
Assumptions & limits
- The formula is an estimate for adult horses of average build. Ponies, foals, drafts and pregnant mares may differ.
- The measurements must be taken carefully and in the same way each time.
- Gut fill and water change the weight through the day.
- Do not use the estimate alone to dose medicines. Use a scale or ask a vet.
- Body condition affects accuracy.
Frequently asked questions
How do I estimate a horse weight?
Square the heart girth in inches, multiply by the body length in inches and divide by 330.
Where do I measure the heart girth?
Around the barrel just behind the elbow and over the withers.
How accurate is the formula?
It is an estimate. A scale is more accurate.
Does it work for ponies?
It may be less accurate for ponies, foals and draft horses.
Why measure more than once?
A small error in girth has a large effect because the number is squared.
Can I dose medicine from this weight?
Ask a vet. Dosing by an estimate can be wrong.
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Last updated: November 2026