To get the most accurate size harness for your pet, measure the girth of their chest, around the widest part of your dog's torso right behind the front legs, with a cloth tape measure. Pull the cloth tape snug, but not tight. If you don't have a cloth tape measure, you can use a piece of string and measure it with a rigid ruler afterwards. Make sure there's enough room for about two fingers between the harness and your pet's chest for comfort.
| Size || Chest Girth |
| X-Small || 9.5 to 10.2 inches |
| Small || 11.8 to 12.6 inches |
| Medium || 14.6 to 15.4 inches |
| Large || 16.1 to 16.9 inches |
| X-Large || 19.7 to 20.5 inches |