Step 1:
Measure your pet from the top of the shoulders to the chest, just behind the front legs. Then measure the width of your pet at the widest point. This will be either the shoulder or hip area.

Step 2:
Determine your pet's weight.

Step 3:
Select the correct door size based on your pet's measurements and weight. You will need a pet door with and opening size that is bigger than your pet's measurement.