Horse Weight Calculator
Estimate your horse weight using the Martinson formula. Enter heart girth, body length, height, and neck circumference to get estimated and ideal weight in kilograms.
About This Calculator
The Horse Weight Calculator helps horse owners, veterinarians, breeders, and equestrians estimate their horse body weight using the validated Martinson formula (2014). Unlike weight tapes that rely only on heart girth, this calculator uses four morphometric measurements — heart girth, body length, height, and neck circumference — for a more accurate estimate of your horse weight.
The calculator uses two formulas. The estimated body weight (EBW) formula is: EBW = (heart girth1.486 × length0.554 × height0.599 × neck0.173) / divisor, where the divisor depends on breed type (3,596 for Arabians, 3,606 for ponies, 3,441 for stock horses). The ideal body weight (IBW) formula uses only height and body length: IBW = 2.8 × length + 4.2 × height − subtrahend, with breed-specific subtrahend values (611 for Arabians, 606 for ponies, 577 for stock horses).
The weight difference between estimated and ideal weight helps assess if your horse is underweight, overweight, or at a healthy weight. A difference exceeding 10-15% may warrant veterinary consultation. Horses greatly vary between breeds — Arabians average around 450 kg while Shire horses can exceed 900 kg — so the calculator provides breed-specific adjustments through the divisor and subtrahend values.
Frequently Asked Questions
How does the horse weight calculator work?
Enter your horse's heart girth, body length, height, and neck circumference in centimeters and select the breed type. The calculator uses the validated Martinson formula (2014) to estimate body weight and ideal weight using morphometric measurements.
How accurate is the horse weight estimation formula?
The Martinson formula was developed from a study of 629 horses and ponies aged 3 years or older and at least 112 cm tall. It provides an estimate within approximately 5-10% of actual weight. For precise measurements, consult your veterinarian.
What measurements do I need for the horse weight calculator?
You need four measurements: heart girth (measured around the girth at the base of the mane hairs), body length (from point of shoulder to point of buttock), height (from ground to third thoracic vertebra), and neck circumference (halfway between poll and withers).
How much does an average horse weigh?
An average riding horse weighs between 900-1,200 lbs (410-545 kg). Arabians typically weigh around 1,000 lbs (450 kg), while draft breeds like Shire horses can reach 2,000 lbs (900 kg). Ponies generally weigh 400-900 lbs (180-410 kg).
What is the difference between estimated and ideal weight?
The estimated weight uses all four measurements to calculate current body weight. The ideal weight uses only height and body length to determine a healthy target weight. A difference of more than 10-15% may indicate underweight or overweight conditions requiring veterinary attention.
Can I use the horse weight calculator for ponies?
Yes, select the "Pony" breed type from the dropdown menu. The calculator uses a divisor of 3,606 for ponies (vs 3,596 for Arabians and 3,441 for stock horses) based on the Martinson study of equids of various sizes.
How can I help my horse lose or gain weight?
For weight loss: increase exercise, reduce high-calorie concentrates and high-fat supplements, feed grass or hay instead of legumes. For weight gain: check for underlying health issues, increase hay, add alfalfa, try performance feed, and allow 24/7 pasture access. Always consult your veterinarian first.
Is the horse weight calculator free to use?
Yes, it is completely free to use with no registration required. You can share your results via the shareable URL that saves your inputs.