How to use the horse weight calculator
- Measure the heart girth with a soft tape.
- Measure body length from the point of the shoulder to the point of the buttock.
- Press Calculate.
Worked example
An adult horse with a heart girth of 170 cm and a body length of 180 cm.
- Heart girth (around the chest behind the withers and elbows)
- 170 cm
- Body length (point of shoulder to point of buttock)
- 180 cm
- Heart girth
- 170 cm (67 in)
- Body length
- 180 cm (71 in)
Estimate for adult horses (Carroll & Huntington 1988). Less reliable for ponies, foals, miniatures and pregnant mares. Never use it to work out medication doses.
Example values are illustrative; this result is produced by the same calculator above.
How we calculate it
Sources: Carroll C.L. & Huntington P.J.
Understanding your result
Not every horse owner has access to a weighbridge, so vets and owners use a tape measure. The heart girth is the circumference around the chest just behind the withers and elbows; the body length runs from the point of the shoulder to the point of the buttock.
The calculator uses a published formula: weight in kilograms equals girth squared times length divided by 11,900, with both measurements in centimetres (Carroll and Huntington, 1988). A girth of 170 cm and a length of 180 cm gives about 437 kg, or roughly 963 lb.
It is an estimate for adult horses. It is less reliable for ponies, foals, miniature horses and pregnant mares, and different breeds can differ by several percent. A weighbridge is more accurate.
Common mistakes
- Measuring the girth too loosely or in the wrong place; take it snugly after the horse breathes out.
- Measuring body length along the back instead of in a straight line from shoulder point to buttock point.
- Mixing centimetres and inches within one calculation.
- Using the estimate for foals, ponies, miniatures or pregnant mares without extra caution.
- Using the result to work out medication or worming doses. Ask your vet.
Good to know
- Measure at the same time of day and with the horse standing square on level ground, so repeat measurements can be compared.
- Track the weight over time rather than relying on a single reading.
- Contact your vet about unexplained weight loss or gain, and before giving any medication.
When to talk to your vet
- Your horse is losing or gaining weight unexpectedly
- Your horse is a foal, pony, miniature or pregnant mare
- Before any medication or worming dose
Frequently asked questions
How do I weigh a horse without a scale?
Measure the heart girth and body length with a soft tape, then use weight = girth² × length ÷ 11,900 with centimetres to get kilograms.
How accurate is the formula?
It is an estimate for adult horses and can be several percent off, especially for ponies, young, miniature or pregnant horses. A weighbridge is more accurate.
Can I use the result to dose medicine?
No. Do not use this estimate to work out medication doses. Your vet will use an accurate weight and the right drug for your horse.
Where exactly do I measure the heart girth?
Around the chest just behind the withers and elbows, snug but not tight, after the horse breathes out.
Does the formula work for ponies and foals?
It is less reliable for ponies, foals, miniature horses and pregnant mares. Use a weighbridge or ask your vet for these.
Why is the result different from a weigh tape?
Tapes are calibrated differently and every method has an error. Use one method consistently and track the trend.
Sources
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Estimate only. Not for working out medication doses; ask your veterinarian. If your pet may have eaten something harmful, contact your vet or an animal poison helpline now.