Horse Weight Calculator
Estimate a horse's weight from heart girth and body length with the standard extension formula.
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What this tool does
Estimate a horse's weight from heart girth and body length with the standard extension formula. Accurate to roughly ±3–5% for typical riding horses; less reliable for ponies, drafts, very fit or pregnant animals. Use the estimate for feed planning — medication and wormer dosing should use the most accurate weight available (a scale beats any tape).
How to use the Horse Weight Calculator
- Enter or select heart girth (inches) in in.
- Enter or select body length, point of shoulder to point of buttock (inches) in in.
- Read the calculated result; change any measurement to compare alternatives.
Formula
estimated weight (lb) = heart girth (in)² × body length (in) ÷ 330 — the widely published university-extension formula behind weight tapes
- girth
- Heart girth (inches) (in, before metric conversion)
- length
- Body length, point of shoulder to point of buttock (inches) (in, before metric conversion)
Accurate to roughly ±3–5% for typical riding horses; less reliable for ponies, drafts, very fit or pregnant animals. Use the estimate for feed planning — medication and wormer dosing should use the most accurate weight available (a scale beats any tape).
Worked example
For horse weight calculator, the following measurements illustrate the exact method: Heart girth (inches): 72; Body length, point of shoulder to point of buttock (inches): 66.
Inputs
- Heart girth (inches)72 in
- Body length, point of shoulder to point of buttock (inches)66 in
Result
- Estimated weight (lb)1,036.8
- Estimated weight (kg)470.28
Results explained
- Estimated weight (lb)
- Estimated weight (lb) from the formula above. Accurate to roughly ±3–5% for typical riding horses; less reliable for ponies, drafts, very fit or pregnant animals. Use the estimate for feed planning — medication and wormer dosing should use the most accurate weight available (a scale beats any tape).
- Estimated weight (kg)
- Estimated weight (kg) from the formula above. Accurate to roughly ±3–5% for typical riding horses; less reliable for ponies, drafts, very fit or pregnant animals. Use the estimate for feed planning — medication and wormer dosing should use the most accurate weight available (a scale beats any tape).
Frequently asked questions
Studies comparing it with scale weights typically find it within about 3–5% for average horses — good enough for ration planning. Weight tapes that use girth alone are a little less accurate than the girth × length version used here.
Heart girth: around the barrel immediately behind the elbows/withers groove, snug on a breathed-out horse. Length: from the point of the shoulder in a straight line to the point of the buttock (tuber ischii), following the body's line with a helper holding the far end.
The constants were fitted on typical light horses. Ponies carry condition differently and drafts have proportionally more mass per girth, so breed-specific formulas exist — for dosing decisions, weigh on a livestock scale if one is available.
Monthly, and whenever condition visibly changes. Seasonal grass changes move weight fast, and feed amounts, worming and transport loading all key off current weight.
Under-dosing wormer encourages parasite resistance, so dose for a weight at the top of your estimate range or confirm on a scale. This calculator gives an estimate, not a scale reading — follow your vet's guidance.