How this calculator works
Minnesota Extension reports breed-group regressions using body dimensions in inches and output in pounds. This calculator converts the selected units before applying those coefficients. Measure height at the withers, heart girth around the chest, neck circumference consistently and length from the shoulder to the buttock. The source population does not justify applying these equations to foals, miniature horses or every breed.
Formula
Current lb = girth^1.486 × length^0.554 × height^0.599 × neck^0.173 / X. X = 119 for Arabians and ponies; 114 for stock horses. Ideal lb = 15.58 × height + 23.52 × length - Y. Y = 1344, 1333 or 1269 respectively. All dimensions are inches; 1 lb = 0.45359237 kg.
Worked example
At 60 in height, 60 in length, 72 in girth and 36 in neck circumference, the Arabian ideal estimate is 1,002 lb (454.4996 kg). The same measurements give 1,077 lb (488.5190 kg) for the stock-horse ideal estimate; current-weight estimates also differ because their divisors differ.
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Frequently asked questions
Can I use the estimate for medication dosing?
Use an appropriate measured weight and veterinary direction. A regression can have substantial individual error and is not a medication plan.
Why does breed group change the estimate?
The source fits different constants to groups with different body proportions. Choose the group that actually fits the horse.
Is ideal weight a guaranteed target?
No. Review body condition, muscle, age and health with an equine veterinarian or nutrition professional before setting a target.