# How to weigh a horse without a scale > How to estimate a horse’s weight with a tape: where to measure heart girth and body length, the formulas for adults, yearlings and weanlings, and how accurate they are. Canonical: https://lucernel.com/guides/weigh-a-horse-without-a-scale Last updated: 2026-10-02 Type: Guide. Publisher: Lucernel. ## Short answer Measure the heart girth and the body length in inches, then multiply girth by girth by length and divide by 330 for an adult horse (301 for a yearling, 280 for a weanling). The result is the weight in pounds. It is closer than a weight tape alone but still tends to read slightly low, so use it to follow changes and ask your vet before dosing a medicine. - **Choose this if:** A tape and a notebook are enough to check one horse now and then. - **Choose the other option if:** Trotley helps when you track several horses’ weight over time next to their feed and health records. ## Side by side | | Tape and notebook | Trotley | | --- | --- | --- | | Estimate from girth and length | Yes, with the formula | Yes, with our free calculator | | Weight history on a chart | No | Yes | | Feeding and health records beside it | No | Yes | | Several horses | Partly | Yes | | Report for the vet | No | Yes, PDF | ## Where to measure - Heart girth: all the way round the body, just behind the shoulder and over the base of the withers, with the tape snug and level. - Body length: from the point of the shoulder to the point of the rump, with the horse standing square on level ground. - Measure in inches for the pound formulas, or in centimeters for the metric one. ## The formulas The Merck Veterinary Manual gives these equations. For an adult horse over two years: weight in pounds = heart girth × heart girth × body length ÷ 330, all in inches. In metric: weight in kilograms = girth² × length ÷ 11,880, in centimeters. For a yearling the divisor is 301, and for a weanling 280. Example: a horse with a 75-inch girth and a 65-inch body length weighs about 75 × 75 × 65 ÷ 330 = 1,108 pounds. ## How accurate it is Merck notes that weight tapes are the least accurate tool and tend to underestimate, and that the girth-and-length formula is closer to the real weight but still tends to read slightly low. Weight tapes also do not suit miniature horses, donkeys or draft horses. The number matters less than the trend. Measure at the same spot, at the same time of day, with the same tape, and a change of a few percent will show. ## What the number is for Weight guides feeding: Merck puts the maximum daily intake of a horse at about 2.5 to 3% of body weight in dry matter, and weight-loss plans are built around current weight. It also guides medication, but ask your veterinarian before dosing from an estimate. Disclosure: Trotley is made by Lucernel, the publisher of this article. ## Frequently asked questions ### How do I calculate my horse’s weight? Heart girth × heart girth × body length ÷ 330, in inches, gives an adult horse’s weight in pounds. Use 301 for yearlings and 280 for weanlings. ### How accurate is a horse weight tape? Tapes are the least accurate method and tend to underestimate. The girth-and-length formula is closer but still slightly low. ### How often should I weigh my horse? Often enough to see trends, for example every two to four weeks, always measured the same way. ### Can I use the formula for a pony or a draft horse? Merck notes that weight tapes do not suit miniatures, donkeys or draft horses; treat girth-based estimates for them with caution. ### Is Trotley available? See the official app page for current availability and pricing. ## Our pick: Trotley, the stable ledger for your horses Trotley keeps each horse’s weight on a chart next to its feed, farrier, dental and vaccination records, so a change shows up before it becomes a problem. - Weight history charts per horse - Vaccination, dental, farrier and medication records - PDF reports for the vet or a new owner [See how Trotley works](https://lucernel.com/apps/trotley) ## Sources (checked 2026-09-26) - [Merck Veterinary Manual: Nutritional requirements of horses](https://www.merckvetmanual.com/management-and-nutrition/nutrition-horses/nutritional-requirements-of-horses-and-other-equids)