A = Length of pet from tip of nose to base of the tail while your pet is standing upright. Do not measure the tail
B = Length of your pets' leg from ground to bottom of chest while your pet is standing
C = This is the widest part of your pet while looking at him/her from the top
D = This is the height of your pet while standing upright. This is measured from the ground to the tallest point of your pet. ie. the top of the head or ears in case they are upright.