When looking at pet door sizes, shoppers see two sets of measurements. The larger numbers are the dimensions of the actual frame, the part that fits into the opening in your door or wall. The second measurement reveals the actual size of the opening the pet will need to fit through, so that's the one with which to take the most care.
Pet doors typically come in small, medium, large and extra-large sizes with a standard measurement ranging from 6 inches wide by 7 inches tall for a small dog door to 17 by 23 inches for a large dog door.
Before settling on a door size, Petsafe.net suggests measuring the animal at its widest point at the chest or hips to determine the correct width of door for the pet. For height, measure the dog from the top of the shoulders to the bottom of the chest or belly, then add 1 or 2 inches.
Sometimes a dog's actual measurements can be misleading, according to petdoors.com's sizing guide (tinyurl.com/m9ml8nh), which outlines a different measuring method. First, open a door as wide as necessary to allow the pet to walk through easily, then measure that opening. The pet door flap needs to be at least that wide. Next, consider the height of the dog. The top of the flap should be mounted at or an inch higher than the top of his shoulder.
Sizing for cat doors is easier to assess since there are two basic choices: Cat doors range from 5 inches tall by 5 inches wide (small) to 7 1/2 by 7 1/2 inches (large). Most cats can go through the small door, although large breeds like the Maine coon cat will need the large door. Tiny dogs such as Yorkshire terriers can usually step easily through a cat door.
-- Rhonda Owen
HomeStyle on 11/08/2014