How to measure a dog for a harness
1) Make your dog stand still and steady. May be you will need somebody's help to hold a dog. It is important for right measurements to measure a steady standing dog.
2) The measurement you will need for any model of harness is chest
circumference (girth). It is measured right behind the front legs,
it is the widest part of dog chest. This line is marked red on the
picture.
3) For some harnesses you will need to know neck circumference. It
is marked green at the picture.
4) Length of chest strap: it is needed mostly for weight pulling harnesses and some other models of dog harnesses which have chest strap. It is marked blue on the picture. Measure it from the line of chest circumference behind the front legs to the same point on the opposite side.