Step 1:
Measure your pet across the widest part of its chest.

Step 2:
Determine your pet's weight.

Step 3:
Select the correct door size based on your pet's measurements and weight.

Step 4:
Do not pick a dog door using only your dogs weight. Measure your dog to make sure they will fit.

Helpful Tip: Get a large piece of cardboard and cut an opening the size of the flap. See if your pet is able to get through this opening. If you get the width right you will be able to adjust the height when you install the door.