Hon, I really couldn't tell you. These were my roommates and she left them! I can tell you some measurements if you like. It is 10 and 1/2 " from the collar the the end of the jacket lengthwise. It is 12 inches all around but it has straps that elongate or go around the belly - so you could use that entire 12" for the back of the dog. I hope I am being clear. My best guess is that if your dog normally fits into a SMALL - he/she will have no problem. Thanks for inquiring and your interest.