About the Horse Weight Calculator
This horse weight calculator estimates body weight from two tape-measure readings: heart girth (around the barrel just behind the elbow and withers) and body length (from the point of the shoulder to the point of the buttock). Enter them in inches or centimetres and choose adult, yearling or weanling to get the weight in pounds and kilograms, plus how much forage that weight typically needs each day.
Most owners do not have access to a livestock scale, yet an accurate weight matters for dosing dewormers and medications, calculating feed rations and tracking weight gain or loss over time. A weight tape alone is quick, but the girth-and-length formula accounts for body length as well and is usually closer for most horses.
The estimate is designed for light horse breeds of average build; draft horses, ponies, heavily pregnant mares and very fit or very thin horses can differ noticeably. For best results measure on level ground, with the horse standing square, and take the girth at the end of an exhalation. Re-measure the same way each time so changes you see are real.
With the default inputs, the estimated weight is 980 lb. Change any value above to recalculate instantly.
How to use the horse weight calculator
- 1Stand your horse square on level ground.
- 2Measure heart girth just behind the elbow and over the withers, after the horse breathes out.
- 3Measure body length from the point of the shoulder to the point of the buttock.
- 4Enter both measurements, choose the unit and age group.
- 5Read the estimated weight and use it for dosing and feeding plans.
Formula and method
This is the widely used girth-and-length formula for adult light horses: square the heart girth, multiply by body length (both in inches), and divide by 330. For young, growing horses a smaller divisor is commonly used — 301 for yearlings and 280 for weanlings. Centimetre measurements are converted to inches before applying the formula.
Forage guidance uses the common rule that horses eat 1.5–2.5% of body weight in dry forage per day, with 2% as a typical maintenance figure, and 5–10 US gallons of water per 1,000 lb in cool weather (more in heat or work).
- heart girth
- Circumference behind the elbow and over the withers (inches)
- body length
- Point of shoulder to point of buttock (inches)
- 330
- Divisor for adult horses (301 yearlings, 280 weanlings)
Worked examples
Adult horse: 70 in girth, 66 in length
70² = 4,900; × 66 = 323,400; ÷ 330 = 980 lb (about 445 kg). At 2% of body weight that horse needs about 19.6 lb of hay a day.
Metric measurements: 185 cm girth, 170 cm length
185 cm is 72.83 in and 170 cm is 66.93 in. 72.83² × 66.93 ÷ 330 ≈ 1,076 lb, or about 488 kg.
Weanling: 50 in girth, 45 in length
Weanlings use a divisor of 280: 50² × 45 ÷ 280 = 112,500 ÷ 280 ≈ 402 lb.
Frequently asked questions
How do I estimate my horse’s weight without a scale?+
Measure heart girth and body length in inches, then use weight (lb) = girth² × length ÷ 330. It is usually within about 5–10% of scale weight for average light horses, which is better than guessing by eye.
Where do I measure heart girth on a horse?+
Run the tape around the barrel just behind the front legs (elbows) and up over the lowest point of the withers. Keep it snug and read it after the horse exhales.
How accurate are horse weight tapes?+
Weight tapes that use girth alone are quick but can be off by 10% or more, especially for long or short-bodied horses. Adding body length with the formula improves accuracy; a livestock scale is best.
How much hay does a horse need per day?+
Most horses need 1.5–2.5% of their body weight in forage daily, typically about 2%. A 1,000 lb horse at maintenance eats about 20 lb of hay a day, more if working or in cold weather.
Does the formula work for ponies and draft horses?+
It is calibrated for light horse breeds. Ponies and drafts have different body shapes, so the result can be less accurate; some owners use breed-specific formulas or a scale for these horses.