Choosing the Right Dog Door
Your pet shouldn't have to squeeze or crouch down to get through the flap. This will cause excess wear and tear, which will decrease the life of the dog door.
Measuring Your Dog For A Proper Fit
The width of the opening in your dog door should be about an inch wider than the widest part of your dog.
Standing face to face with your dog... measure your dog at her widest point from left to right and add an inch.
To determine the height of the dog door opening you'll want to measure from the top of your dog's shoulders to the underside of her chest just behind the front legs and add an inch.
Now using these two measurements... draw a box on a piece of cardboard. Then cut out the box shape and see if your dog can easily walk through the cut out in the cardboard template.
Your dog must be able to comfortably pass through this cut out. If she can't… re-measure and try again until you get a proper fit.
The dimensions of the dog door you choose must be equal to or larger than these measurements or the opening will be too small for your dog.
Determining The Proper Dog Door Installation Height
It's recommended that you install your dog door so that the topmost part of the opening is no lower than the top of your dog's shoulders.
The installation height of a panel pet door for a sliding patio door is predetermined.
So make sure that the height of the opening plus the "rise" is at least equal to the height of your dog's shoulders. The rise is the height of the step-over for your pet.