What's the Best Way to Estimate a Horse's Weight?

Q. I’m trying to estimate my horse’s weight to determine how much hay, grain, and other products I should be feeding. I bought a weight tape at the feed store and it says that he weighs 1,050 pounds. However, he looks heavier than that to me—he’s a heavily built Quarter Horse. My friend let me borrow a different weight tape, and that one and it says he is 1,125 pounds. That seems closer although I still think he weighs more. How am I supposed to accurately determine his weight if the tapes say different things?

A. Weight tapes are a very useful tool for estimating a horse’s weight; however, as you have found, they do differ and aren’t always accurate. Different tape manufacturers use slightly different algorithms to convert the distance around the horse’s heart girth into a body weight estimate. I own several different tapes and each one gives a different weight when used on the same horse.

Fortunately, there are some things you can do to get the most accurate estimate. Have the horse stand squarely on level ground and be certain to place the tape correctly on the horse. Unless the tape gives other directions, place it around the horse’s entire barrel about an inch below the highest point of the withers and tightly behind both elbows. The tape should be in a vertical line when the horse is viewed from the side. Check to make sure that the tape is not twisted on the opposite side of the horse.

I generally find the tapes I have provide a fairly accurate estimate for a horse with proportional conformation and of moderate size, but that they underestimate the weight of those that are long backed or particularly tall. I find that regular tapes also tend not to be as accurate on Miniature Horses and small ponies either.

While tapes are a good tool for monitoring relative weight gain or loss over time, my preference is to use a weight calculation formula, as this is typically found to be more accurate. This calculation requires the same heart girth measurement, although in inches, in addition to a length measurement from the horse’s point of shoulder to point of buttock. Once you have these two measurements you can plug them in to a weight calculator, like the one on available at TheHorse.com/WeightCalculator, which will then estimate your horse’s weight.

I like to compare the calculated weight against the weight given by the tape to see how they differ. Again, the calculation method is less accurate for very tall horses and is not designed for use in estimating Miniature Horses’ weights.

Of course, the most accurate way to measure body weight is to use a scale, but few of us have easy access to one. Your veterinarian might have one available at their practice. If they do, I recommend my clients weigh their horses whenever they take them to the clinic for routine visits.

If your veterinarian does not have a scale available, there might be other scales in your community that you can use. For example, look for a weigh station at a truck stop. You will need to drive your truck and trailer to the station empty and weigh it to determine the tare weight. Then return with your horse in the trailer and weigh again. Subtract the empty weight from the loaded weight to determine your horse’s weight. Some companies have truck scales and might be willing to let you use them, so ask around to find out what might be available in your area.

With an accurate scale weight, you can determine how accurate your weight tape is really is. You might find that if you slightly tweak the tape placement on the horse you can match the scale weight. This should give you more confidence when you use the tape to monitor body weight. Ideal placement can be hard to determine in some horses depending on their wither conformation, and this likely contributes to some of the calculation error.

Once you have determined as accurate a body weight for your horse as possible you will want to use body condition scoring to confirm whether they should gain, lose, or maintain their current weight. Ensure you’re feeding a minimum of 1.5% of body weight per day as forage and, if you’re feeding a commercial feed, be sure that you’re going so per the manufacturer’s directions for your horse’s body weight and work level. This will help to ensure a balanced ration that meets nutritional requirements.