When sizing, the most important factor is the chest measurements. These measurements ensure that your dog can move properly while wearing the coat. Once the chest girth is determined, you can review the back length according to our Fitting Room guidelines. If there isn’t a precise match, we do recommend that you choose the shorter length rather than the longer one to ensure a snug fit. The next step is to measure the neck. This will help ensure that the fit is not too tight in that area. Our Chilly Sweaters and Great White North coats have more stretch through the neck in comparison to our Rain Slickers and Blazers. This is due to the polar fleece which will be able to accommodate a larger neck size. Another important factor to consider is the weight of the dog. However, it should be used as a guideline, not a defining factor since dogs come in all shapes and sizes. If you have any questions or if you are uncertain about which size to choose, please contact us at firstname.lastname@example.org. We will be happy to go over the measurements with you to ensure your dog gets the best fit. We are also available by phone at 1-844-364-2628 M-F, 9am-5pm ET.