What Size Dog Door Do I Need?

Mia Daniele

As pet owners, we want nothing less than the best for our dogs and cats. We want them to have the best food, the best walks, and of course, the best scratches.

That’s why it’s important to make sure that you have the best pet door for you and your pet. That means making sure that your pet door is the right size for your dog.

A pet door is a great way to provide your pet the freedom to come and go as they please. Maybe your cat is walking all over your keyboard, or your typically calm dog breed is letting out excess energy running all over the house. A pet door can help fix these problems by providing your pet a healthy outlet for their energy by exploring the backyard whenever they choose.  

Read on to find out about the importance of having a properly sized pet door and how to find out what size dog door you should get.

Border collie laying down and looking up at the camera

Why Does My Pet Door Need to Be the Right Size?

Your pet door will be something that your dog will use every day, so it’s important that it’s comfortable for them to use. This means making sure that the door is the right height and the proper size.

If your pet door is too low, the top will scrape against your dog’s back. This can hurt your dog and even contribute to long-term medical problems. Plus, if your door is too low and causes discomfort, then they will be hesitant to use their new door.

That means the effort to cut a hole in your wall for an in-wall pet door or to measure your sliding door track for your patio door insert would be wasted, as you would then need to readjust the position of your door or get a new one entirely.

While it might seem safer to go bigger with your door flap, getting one that’s too big is a problem as well. If your door is door big, even the most lightweight of flaps can be difficult for smaller dogs and cats to push open.

Additionally, the Dragon Pet Door has magnets on its flap and gasket to help seal it against extreme cold weather. A bigger flap means more magnets, which means that it can be harder for smaller and weaker pets to push through the flap.

Between causing discomfort to your pet and difficulties using the flap, it’s important to ensure that your pet door is the right size. Note that pet doors are like clothes—different sizes mean different things between brands.

You can’t even base it on the average size of a dog, their weight, or their breed as dogs of the same breed might be different heights based on gender and age. That’s why it’s best to measure your dog for their new pet door instead of relying on estimation or prediction.

Cat's have a little more flexibility when it comes to pet door size. We all know that cats can fit into very small spaces (have you ever seen a cat squeeze into a tiny box?). Cats will typically have an easier time fitting through smaller flaps, but it's still important to measure to make sure they can use their new door comfortably. 

cat using a properly sized cat flap installed into a wall

How to Find the Right Door Size

Even though it’s very important that you find the correct pet door measurements, it’s not actually that hard to do! All you need to start is your cat or dog’s measurements. From there, you can easily find the correct pet door size with some easy steps:

Step 1: Find your pet’s height. Take a tape measure and measure their front paw to the highest point of their back. This measurement is their height.

Step Two: Calculate the step-over. Your pet door is not going to be right at floor level. It will at least be a couple of inches off the ground; this distance is your step-over. If you have a smaller pet, the step-over will be about 2-3”, while bigger pets can step over around 4-5” (make sure that the step-over isn’t too high, or else your dog will have problems using the door when they are older).

Step Three: Find your pet door. Dragon Pet Door has a variety of pet door sizes, making it easy to find the right door for you. To find the right size, look at the height of the pet door flap on the pet door size chart:

Door Size Flap Dimensions
Medium 7" w x 13 1/10" h
Large 9 2/5" w x 16 3/5" h

 The total height of your door with the step-over should be at least one inch above your dog’s back. So if you have a dog that is 12” tall, you will need a pet door that’s total height with the step-over is 13”. The Dragon pet door in medium is 10” tall. With a 3” step-over, it will be tall enough for your dog.

A great pet door option is the Dragon Pet Door for Doors. Choose between a Medium and Large flap to fits small to medium-sized dogs. The Dragon Pet Door for Doors is available in a single or double flap to match your insulation needs.

The flap is the same size for the single and double flap—just follow the measurement guidelines from this guide in this article or reach out to customer service and we'll help you find the perfect fit.  

dragon pet door for doors - choosing pet door size


Step 4: Test the pet door size. If you’re uncertain if you have the right size or not, you can test it before you buy it. Make a hole in a piece of cardboard that is the extract dimensions of the pet door plus its step-over. Then, have your dog walk through it. You can see before you buy it if the pet door is tall enough, or if you need to adjust the step-over height.

And that’s it! With these steps, it’s easier than ever to find the doggie door size that is the right size for you. If you have any problems finding the right door, you can always ask our customer service team for advice.

Mia Daniele

Written by

Mia Daniele

Copy Editor

Pets: I have a fluffy, 14 year old chow-collie mix with red fur named Rosso. He's very stubborn and has the standoffish personality of a cat.
Fun stuff: I am a hot chocolate connoisseur.

Copy Editor

Pets: I have a fluffy, 14 year old chow-collie mix with red fur named Rosso. He's very stubborn and has the standoffish personality of a cat.
Fun stuff: I am a hot chocolate connoisseur.

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