It’s important to know your horse’s weight if you are administering a medication, supplement or dewormer. It’s also useful to know how to estimate your horse’s weight so you can monitor it over time and catch any weight changes early.
The most accurate way to determine a horse’s weight is by weighing him on a scale but this is not a practical solution for most horse owners. Fortunately, we can closely estimate a horse’s weight by using body measurements. While horse weight tapes that require only a heart girth measurement are readily available, studies have shown that using a combination of heart girth measurement and body length plus a simple calculation usually gives a more accurate estimate.
It helps to have a second person to help with these measurements because it may be difficult for one person to reach far enough to get accurate measurements. And note that for the heart girth measurement, the tape goes all the way around the horse. You can use a regular measuring tape (a vinyl or fabric one is easier and more accurate than a metal tape). So let’s get started with the measurements.
Heart Girth: To measure a horse’s heart girth, place the end of the tape at the middle of the withers, run it down one side of the horse to just behind his front legs (where the girth would go) and straight up the other side back to the withers. Where the tape meets is the heart girth measurement. Write down or remember that number.
Body Length: Measure from the point of the shoulder to the point of the buttocks (tuber ischii). This measurement is just on one side of the horse. Write down or remember that number.
Then do this simple calculation:
Horse weight = Girth X Girth X Body Length ÷ 330
For example, if your horse’s heart girth measurement is 76 and body length is 70, your calculation would be 76 X 76 X 70 ÷ 330 = 1225 lbs
This is the formula for calculating the weight of an adult horse. For a yearling, divide by 300 and for a weanling, divide by 280.