The cinch is the padded strap that holds a horse's saddle in place. Accurately measuring the cinch ensures it will be tight enough to keep the saddle in the proper position but loose enough to ensure comfort for the horse. The cinch size is measured around the barrel, or body, of the horse, just behind the front legs and withers. The withers is the small hump located at the base of the horse's neck, just about where you would expect the shoulders to be.
Lead the horse to a level area. Move to the horse's left side.
Wrap a cloth tape measure around the horse's body. The tape measure should lay at the base of the withers and just a few inches behind where the front legs join the body. The tape measure should appear to be at a slight backward angle. Read the measurement.
Divide the measurement by 2 and subtract 3. If the result is not a whole number, round up. As an example, if you measured 75 inches on your horse, you would divide that number by 2 to get 37.5. Then, subtract 3, which gives you the cinch size as 34.5 inches. However, this is not a whole number, so round up to 35 inches. In this case, you would use a cinch 35 inches in length.