If you have a soft (Tailor) Tape measure, follow the sizing guides and instructions when measuring your dog. If you don't have a Tailor Tape, take a strand of string and wrap it around the area of your dog indicated by the sizing guides. Mark the sting and cut it. Then, place the string beside a tape measure to properly indicate the length. You should measure your dog before placing an order to avoid returns. The weight section in the size guides is for rough approximation.