NOTE THE SIZING RUNS SMALL, IF YOU'RE IN DOUBT ORDER UP A SIZE
Measure guide: Put your dog on a firm, flat surface with a piece of paper under their front paws (the front paws tend to be bigger). Using a pencil, outline the shape of the paw (including the nails), measure the width and length and check against the image size chart. If you're unsure we would recommend ordering up a size to be safe.
Small: front paw 30-40mm wide x 25-35mm long
Medium: front paw 35-50mm wide x 35-50mm long
Large: front paw 45-65mm wide x 45-60mm long
XLarge: front paw 55-80mm wide x 55-70mm long
If your dog is long haired take this into consideration and go up a size. The lycra in the socks allows them to be stretched more than double the width, when fitting on your dog to ensure a secure and comfortable fit.