Properly Sizing a Dog Door
The Easy Way:
The simplest way to ensure that the pet door you get will fit all of your pets comfortably is to test the opening size before you buy. Get a piece of cardboard, cut a hole that is the size of the flap dimension in the cardboard, stick it in a doorway, and call your pets through to make sure that they are comfortable. If you are considering a panel pet door for a sliding glass door, cut the hole to simulate the rise, e.g. if you are thinking of a 5" rise, cut the hole 5" from the bottom of the cardboard.
The Hard Way:
Step 1: Find out your minimum flap width for your widest pet.
Measuring your dog or cat will lead you to believe you need a much larger door than is actually necessary. Harley pictured near the bottom of the page measures 15" from the tip of her fur on one side to the tip of her fur on the other, but she can run through a 10" door at full speed. The easiest way to get an accurate measurement is to open a door just wide enough that your pet can get through, and then measure the width of that opening. This is your minimum flap width, you can add an inch to make things more comfortable.
Step 2: Measure your tallest pet's height.
Measure your pet to the top of his/her back at the front shoulder. The top of the pet door flap should be at or slightly above this height.
Step 3: Measure your shortest pet's clearance height.
Take a measurement from the floor to your shortest pet's chest. This is the clearance, and your pet door flap should start at or slightly below this measurement. On a pet door for a wood or steel door, you can choose to mount the pet door at whatever height is comfortable for the animals within reason; we recommend you cut no closer than 3" from the bottom. On sliding glass door panels the distance from the floor to the bottom of the flap is called the rise measurement and is a fixed height (not adjustable).
If your pet is not fully grown:
To estimate the adult size of your puppy or kitten refer to the breed standards. If in doubt call us, we have some good reference material that can help to make the right decision.
Getting it Right:
This is what a properly sized and installed pet door should look like. The 11" width flap suits the Golden Retriever just fine. The height of the flap is 16 inches, and it is set up off the ground so that the flap is just an inch or so above the dog's shoulder height. Stepping over the 8 inches from the floor to the bottom of the flap is no problem for a dog this size. But what should you do if you have more than one pet, in more than one size???
Let's suppose you are the proud owner of Harley the mixed breed, Brady the Corgi, and Isaac the German Shepherd. You need to find a pet door that will fit all 3 dogs. Harley is, well… a little chubby. She requires at least a 10 inch wide opening, but would prefer 11 inches. Brady is a short dog with only 4 inches of clearance. And then there is tall and lanky Isaac, who stands 27 inches at his shoulder. Which door fits all of these dogs? A Hale Extra Tall Large for a door or wall installation, or a Thermo Panel 3e or Quick Panel 3 for the slider, as these have flaps tall enough for Isaac that can be located low enough for Brady, and wide enough for Harley.