Our number sizes refer to the top line of the dog. The top line is the measurement from the base of the collar to the base of the tail along the back as shown above. So if your dog measures 14", most likely the 14" sweater would fit. However, you do need to take into consideration if the dog has a lot of fluffy hair or is overweight......then you may want to go up a size. We are always happy to help you if you have questions. You can call us at 972-965-4981.