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Measure Your Pet For A Pet Door

"What size pet door do I need?" Whether you have a small dog, a large dog, or a polar bear-sized pooch, we can tell you how big your pet door needs to be!

How to Measure

Measuring your pet's height correctly is crucial in ensuring you purchase a flap that your pet can comfortably use their entire life.

You need to keep in mind how high off the ground the dog door will be installed; this space between the ground and the bottom of the flap is called the Step Over.

The Step Over should be as low as possible for your dog to go through comfortably, as your pet gets older they may begin to find it difficult to get through a door with a high Step Over.

Backyards and patios are typically a few inches lower than a home's floor level. Please make sure that your dog is comfortable stepping over both the step-over and the extra distance between the floor-level and the ground outdoors (this is more important for doors with large step overs or for tiny dogs).

1. Measure Your Pet’s Height

  • Stand your pet up straight.
  • Measure from the ground to the tallest point of your dog's back (this may be their shoulders, mid-back, or tailbone).

2. The Top of The Flap Should be At Least 1” Taller Than Your Pet's back

  • Even smaller dog’s have a tendency to barge through small doggie doors. If the top of the flap isn’t tall enough, your pet may be hurting their back every time they go through the door. You also don't want a dog's collar getting caught on the top of the door, as it'll wear out the door and could hurt your pet!

3. The Step Over Height Should Never Be More Than 1/3rd of Your Pet’s Height

  • Door mounts typically require a step over of at least 3” to not ruin the integrity of the door.
  • The step over should be as low as possible for your pet to comfortably get through , this will make it easier as they get older.

4. Measure Pet Door Width

  • Measuring how wide of an opening you need can be done by blocking off a portion of your doorway and leaving only the intended width open and calling your pet through. This will let you know if your door is too small with your dog's width. They should be able to fluidly move through the door.

5. Create Mock Pet Door on Cardboard

  • Once you have determined the dimensions of the pet door you need, we recommend taking the dimensions of the flap and replicating them into cardboard and seeing if your pet can go through. This isn't always necessary, but is a good way to ensure that there are no doubts!

Multiple Pet Homes

When multiple pets are sharing a pet door, it is important to take into account that all of your pets should be able to use the pet door comfortably.

You will need to take the measurements of your largest and smaller pet. You need a pet door that has a flap height that is at least 1" taller than your largest pet, and a step over no more than 1/3rd of your smallest pet's height from the floor to their back. This will give you the best dog door size for your household!

How to measure for dog door size starts with your pet's  height from feet to shoulder Dog door flap size

Large dogs are not always standard, check out this example and see what size they need

Thanos & Loki

Height: 23"
Width: 10" [Thanos] 9" [Loki]
Maximum Recommended Step Over: 7"

Their pet door:
Endura Flap size Large

Medium dogs can be tall but still need a smaller pet door


Height: 20"
Width: 7"
Maximum Recommended Step Over: 6"

Her pet door:
Endura Flap size Medium

small dogs like Louie do not always need a door size as big as them


Height: 12"
Width: 4"
Maximum Recommended Step Over: 4"

His pet door:
Endura Flap size Small

What Size Dog Door Should you Get?

Dog Requiring Low Step Over | Let's say your dog is 15" tall, and needs a pet door at least 8" wide to comfortably pass through. Your dog also suffers from arthritis, so he needs the Step over to be as low as possible. You will be installing the pet door through a wall, so you can build a ramp to make the Step over just 1". Your pet door flap size needs to be at least 16" tall, and 8" wide, so you will require a tall pet door, but not too wide. Hale has the perfect pet door with a flap size of 8.5" x 16"!

Tall Dog | If you have a very tall dog with long legs with no health issues, they might be able to easily step over a height of 7"-10" for their pet door. Let's say your dog measures 29" tall, and needs an opening at least 10" wide to be comfortable.
An economy level option would be the Ideal Ruff Weather in Super Large, which is 15" x 23.5". It would need to be installed at least 6.5" off the ground for the top of the flap to be 30" from the ground!The Endura Flap in Extra Large is 12" x 23", and though it would need to be installed 7" or higher from the ground you would have 3" less of unnecessary width.

Measuring your Cat | When it comes to measuring cats, it can be more difficult to get them to stand still. The easiest way to test flap size for them is to cut a hole in a piece of cardboard that is the size of the flap you are interested in, then coax them through with treats. Place the cardboard in the opening of a door, so they have to walk through the hole to get to the reward!

How to measure cats for cat doors starts with a mock cutout

Big and Small Pets Sharing | You'll need to select a size large enough to be installed with the top high enough for your tallest pet and the bottom low enough for your smallest pet. You'll also need to take into account the type of flap, as some large flaps might be too difficult to open for little guys. Hale makes a great flap for those who need to share!

the endura flap pet for doors with a double flap model

Endura Flap Pet Door for Doors

the ideal ruff weather pet door with a black tinted flap and a plastic frame

Ideal Ruff Weather Pet Door

the liberty pet door with a wood frame and a clear vinyl flap

Liberty Pet Door for Walls

Still Confused?

If you are still unsure what flap size would be best for your pet(s), don't hesitate to contact us. See if we're available on our live chat in the bottom right corner of your screen or send us an email. Have your pet's measurements handy to better help you find the right size.

How big will my dog get?

That's a great question! No one really knows, but you can make an educated guess. If you know the parents, you can get an estimate based on the parent of the same sex; this is the best way to measure your dog for doggie doors they will need to grow into. If you don't know the parents, you can do a web search on the breed/gender to get an estimate. Read all about it in our blog post about How Big Your Puppy Will Be.

Are all brands' small - large the same size?

No, every brand has different measurements for their pet door sizes. The flap door's opening size will also change, as the aluminum or plastic frames change in width and design.

Why are larger pet doors more expensive than smaller ones?

Mainly due to materials and manufacturing. It costs more money and uses different machinery to make larger dog doors, so different sizes have different costs. The same goes for the quality of the doors. Larger, high-quality doors that take into account energy efficiency will cost more than an economical one.

What does flap dimension mean on the size chart?

For most manufacturers, the flap dimension is the height and width of the door opening. This is the actual opening your dog walks through.

How do I measure my pet for a sliding glass door dog door?

For patio doors, sliding doors, and French doors, the measuring process is just about the same. That being said, a lot of patio panels have fixed step-overs, so you need to take that into account and may end up with a larger dog door size than if it was a door or wall mount.

Does this measuring guide work for cats and cat doors?

Yes! The way that cats move through a cat door or cat flap is different than a dog, but they have the same principle in regards to sizing. Cats also tend to be able to get through any sized hole, so as long as the door isn't smaller than their head, your average cat will be able to get through it.