Instructions
With a tape measure, measure the horse's "heart girth" (in inches). The girth is the circumference of the horse's torso, measured from the base of the withers, down to a few inches behind the front legs, under the horse's belly, then up the other side to your starting point. Your tape measure may run at an angle.
Measure the horse's length, from the far end of the shoulder to the far end of the hip. Again, the tape measure may run at an angle.
Take the heart girth (for example, 60) and multiply it by itself (60 x 60 = 3600).
Multiple the result by the length (for example, 50 (3600 x 50 = 180000)).
Divide the result by 300 (180000 / 300 = 600).
Add 50 (600 + 50 = 650). You horse should weigh 650 pounds.
How to Use a Tape to Weigh a Horse
Horses are beautiful creatures but they require maintenance--feed, medication, and so on. To plan a horse's upkeep, it is helpful to determine its weight. Lacking a gigantic scale, however, use a simple tape measure to do the job with ease.