Horse Weight Calculator
Estimate a mature horse's weight from heart girth and body length using the standard weight-tape formula, in both pounds and kilograms.
How it works
Weight (lb) = (heart girth² × body length) ÷ 330 · Weight (kg) = pounds × 0.4536
Without a livestock scale, the reliable field method is a body-measurement formula. Heart girth — the circumference just behind the front legs — captures the horse's barrel, and because weight tracks a cross-sectional area, that measurement is squared before multiplying by body length from the point of shoulder to the point of buttock. Dividing by 330 (with both measurements in inches) converts the result to pounds. It is an estimate calibrated for mature light-breed horses and typically lands within about 5–10% of a true scale reading, close enough for dosing wormers, feeding by body weight and tracking condition. Foals, ponies and heavy draft breeds have different proportions, so specialised formulas serve them better.
Worked example
A horse with a 72-inch heart girth and a 66-inch body length weighs about (72² × 66) ÷ 330 = (5,184 × 66) ÷ 330 ≈ 1,037 lb, which is roughly 1,037 × 0.4536 ≈ 470 kg.
Frequently asked questions
Where exactly do I measure the heart girth?
Wrap the tape all the way around the barrel just behind the front legs and withers, snug but not tight, ideally when the horse has exhaled. This girth measurement matters most because it is squared in the formula.
How accurate is this estimate?
For mature light-breed horses it usually falls within about 5–10% of a livestock scale — accurate enough for feeding, medication dosing and monitoring condition, but not a substitute for a real weighbridge when precision is critical.
Does it work for ponies and draft horses?
Less well. The divisor of 330 is calibrated for average adult riding horses. Ponies, foals and heavy draft breeds have different body proportions and are better served by formulas or weight tapes made for them.
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This calculator is for educational purposes. Double-check important results before acting on them.