Back: Measure length of petís back from the base of the neck to the base of the tail. See below for estimating by breed.
Neck: Measure the circumference of pet's neck for a snug fit. No need to add inches as you would with a collar.
Chest/Girth: Measure girth around the broadest part of the chest and add 2".
Note: If the dog has a stout build, select one size larger.
Recommended sizing by breed:
X-Small: Australian Terrier, Chihuahua, Pomeranian, Toy Poodle, Yorkshire Terrier
Small: Boston Terrier, Brussels Griffon, Jack Russell Terrier, Lhasa Apso, Maltese, Miniature Pinscher, Norfolk Terrier, Papillon, Pug, Silky Terrier
Medium: Bichon Frise, Beagle, Cocker Spaniel, Corgi, Scottish Terrier, Shih Tzu, West Highland Terrier, Whippet
Large: Brittany Spaniel, Bulldog, Collie, Schnauzer, Springer Spaniel
X-Large: Australian Shepherd, Border Collie, Dalmatian, Golden Retriever, Vizsla, Weimaraner