Details: Length – 26 inch Girth Circumference of chest- 24 inch Measure your dog s length. Place the beginning edge of the measuring tape at the base of the neck, where it joins the shoulders (the nape of the neck). Extend the free end of the measuring tape along the length of the spine until it reaches the base of the tail. measure your dog s girth. Get your dog to stand up so that you can measure the circumference around his ribcage (the girth). Try to measure the widest part of the dog s chest, which is generally located just behind the points of the elbows.