Horse Weight Estimator (Heart Girth & Body Length Calculator)
Estimate horse body weight from two simple tape measurements - heart girth and body length. Uses the Carroll & Huntington equation, separately calibrated for adults, yearlings, weanlings and ponies.
Measurement units
Life stage
Heart girth (in)
Measure around the chest just behind the elbows, at the deepest part.
Body length (in)
Point of shoulder to point of buttock (tuber ischii).
How to use this tool
The formula
Body weight (lb) = (heart girth² × body length) ÷ divisor. The divisor changes with life stage: 330 for adults, 301 for yearlings, 280 for weanlings, 299 for ponies. All measurements in inches; centimeters get converted internally.
How to measure correctly
Heart girth: circumference of the chest just caudal to the elbows, at the deepest part of the chest. Tape should sit snug against the body. Bring it together on top of the withers.
Body length: from the point of the shoulder to the point of the buttock (tuber ischii). This is the long axis of the body, not from poll to tail.
Accuracy and clinical use
Expect ± 10% accuracy compared to a livestock scale. Good enough for general dosing approximation, body-condition monitoring, and feed planning. For chemotherapy or other narrow-margin drugs, weigh on a scale.
Frequently asked questions
How accurate is the heart-girth weight estimate?
Typical accuracy is ± 10% compared to a livestock scale. Good enough for dosing approximation, feed planning and body-condition trending. For chemotherapy or other narrow-margin drugs, weigh on a scale.
Where do I take the measurements?
Heart girth: circumference of the chest just behind the elbows, at the deepest part. Body length: point of shoulder to point of buttock (tuber ischii). Use a soft cloth tape and keep it snug but not compressing.
Why does the divisor change with life stage?
Yearlings, weanlings and ponies have different body proportions than adult horses. The Carroll & Huntington study calibrated separate divisors so the formula works for each life stage: 330 (adult), 301 (yearling), 280 (weanling), 299 (pony).