Picking the right size is the single most important part of choosing a pet door. Too small and your pet won't use it comfortably; too large and you give up security and energy efficiency. The good news: it comes down to just three measurements, and you can take them at home in five minutes.
1. Width (the easy one)
Measure the widest part of your pet — usually the shoulders or hips — while they're standing. This tells us how wide the flap opening needs to be. Round up slightly; pets should never have to turn sideways or squeeze.
2. Height (shoulder to floor)
Measure from the top of the shoulders straight down to the floor. Combined with the step-over below, this sets how tall the flap needs to be and where it sits in the door or wall.
3. Step-over (the one people forget)
This is the height from the floor to your pet's belly/chest — the height they can comfortably lift a paw over. The bottom of the flap is set at or below this line so older pets, short-legged breeds, and cats can step through easily without hopping. Get this wrong and even a big door feels awkward to your pet.
A few real-world tips
- Measure the pet, not the pet you think you have. Fluffy coats and a little extra weight change the numbers.
- Growing puppy? We size for the adult dog so you install once.
- Two pets of different sizes? We size to the larger one, and the smaller pet manages the flap just fine.
- When in doubt, size up a little. Comfortable beats snug.
Why we still measure in person
You can absolutely take these numbers yourself, and it helps you understand the recommendation. But when we come out for your free assessment, we re-measure your pet and the exact door or wall, then match it to the right product — because the flap size, the frame, and the mounting height all have to work together. It's the difference between "about right" and "perfect."
Want more detail on flap dimensions and fit? See our sizing guide and the full pet door resources page. When you're ready, we install across Georgia — get your free quote.
