How To Measure Your Pet
The Neck is measured at the place where your dog's collar would naturally rest - from about the top of the chest to just above the withers (the high part of the back between the shoulders where the neck joins the body) this measurement is also taken all the way around.
The Girth (or Chest) measurement is taken all the way around the biggest part of your dog's ribcage, generally just behind the withers down and around just behind the front legs and back up the other side.
The Back (or Topline) is the length of your dog's back, measured along the top of the spine from the withers to the base of the tail where the tail joins the body.