If your dog is on the border between sizes, we usually say go for the larger size. Many dogs can fit two sizes. It’s not an exact science and the coats are very adjustable. The bigger size will cover and dry more of your dog. But, when choosing the bigger size, do consider carefully if your dog is very small, short legged, excitable or has a stick-up tail, as in these cases it is less easy to go for the larger size!