Horse Weight Calculator
Estimate your horse's weight from heart girth and body length using the standard equine weight formula. Free horse weight calculator in pounds and kilograms.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Horse Weight Calculator Works
This calculator estimates a horse’s body weight from two simple measurements, the heart girth and the body length, taken in inches with a soft measuring tape. It returns the weight in both pounds and kilograms, and lets you pick the right divisor for an adult horse, pony, yearling, or weanling.
A livestock scale is the only exact method, but the girth-and-length formula is well established in equine practice and is usually accurate to within about 5 to 10 percent, which is fine for feeding, deworming, and body-condition monitoring.
The Formula
For an adult horse:
Weight (lb) = (heart girth in² × body length in) ÷ 330
To convert to kilograms, multiply pounds by 0.4536. The divisor depends on the horse’s age and type:
| Horse type | Divisor |
|---|---|
| Adult horse | 330 |
| Pony | 299 |
| Yearling | 301 |
| Weanling | 280 |
Worked Example
For an adult horse with a heart girth of 72 inches and a body length of 63 inches:
- Girth squared = 72 × 72 = 5,184
- 5,184 × 63 = 326,592
- Weight = 326,592 ÷ 330 = ≈ 990 lb
- In kilograms = 990 × 0.4536 = ≈ 449 kg
How to Take the Measurements
- Heart girth — wrap the tape around the barrel just behind the front legs and over the withers, where the saddle girth sits, and read the full circumference.
- Body length — measure the straight-line distance from the point of the shoulder to the point of the buttock (the bony point of the hip).
- Use a flexible cloth or fiberglass tape, and have the horse stand square on level ground for the most consistent reading.
Why Knowing the Weight Matters
- Medication and dewormer dosing is almost always per pound or kilogram, so a good estimate avoids under- or over-dosing.
- Feeding rations of hay and grain are set as a percentage of body weight, typically 1.5 to 2.5 percent per day.
- Body-condition tracking is easier when you weigh consistently with the same method over time.
Frequently asked questions
How do you calculate a horse's weight?+
Measure the heart girth and body length in inches, then use weight in pounds = (heart girth² × body length) ÷ 330 for an adult horse. For a horse with a 72-inch girth and 63-inch length, that is (72² × 63) ÷ 330 ≈ 990 pounds.
Where do I measure the heart girth and body length?+
Heart girth is the circumference around the barrel just behind the front legs and withers, where a saddle girth sits. Body length is the straight-line distance from the point of the shoulder to the point of the buttock. Measure both in inches with a soft tape.
Why does the formula divide by 330?+
The divisor reflects the typical body density and shape of an adult horse. Different growth stages use different divisors: 330 for adult horses, 301 for yearlings, 280 for weanlings, and 299 for ponies, which improves accuracy for each body type.
How accurate is this horse weight estimate?+
The girth and length formula is usually within about 5 to 10 percent of a livestock scale reading, which is accurate enough for routine feeding and deworming decisions. A calibrated scale is the only exact method; very fit, pregnant, or unusually built horses may vary more.
Why do I need to know my horse's weight?+
Accurate weight is essential for dosing dewormers and medications, calculating feed and hay rations, monitoring body condition, and safely loading for transport. Most equine medications are dosed per pound or kilogram, so a good estimate prevents under- or over-dosing.