Measure length of pet's back from the base of the neck to the base of the tail. If the measurement is between sizes, we recommend going up one size. Also, if pet has a stout build, a deep chest, or is overweight, we recommend going up a minimum of one size for proper fit. If the dog is long-backed, like a Dachshund, a smaller size is recommended.

X-Small fits up to 8"
Small fits 8"-12"
Medium fits 12"-16"
Large fits 16"-20"
X-Large fits 20"-24"