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How to Choose a Pet Door
A pet door is the rare upgrade that changes your daily life — no more 6 a.m. wake-ups to let the dog out, no more scratched paint by the back door. But cut the wrong hole in the wrong place and you’ve got a drafty, leaky, break-in-friendly hole in your house. Getting the size, mounting type, and flap system right is the whole game.
The short answer
Measure your pet’s shoulder width and step-over height first, then pick a flap one size up. For most homes a dual-flap, door-mounted model with a locking slide is the sweet spot — weather-tight enough for real winters, simple enough to install in an afternoon. Go electronic (microchip- or collar-triggered) if strays, raccoons, or a nervous neighbor cat are a concern.
Start with the pet, not the door
Every sizing mistake traces back to skipping this step. You need two numbers: your pet’s shoulder width (the widest part that has to fit through) and their step-over height (measured from the floor to the top of their back, so you know how high off the ground the flap opening should sit). The flap opening should be at least as tall as your pet at the shoulder, and the bottom of the flap should sit no higher than the tallest pet’s belly — low enough to step over comfortably, high enough to keep drafts and floodwater out.
Buy for the biggest animal that’ll use it, and if you have a growing puppy, size for the adult. When you’re between sizes, go up: a slightly loose flap is a minor annoyance, a too-small one is a door your dog refuses to use.
Where it mounts changes everything
The mounting type dictates the hardware, the difficulty, and whether you should call a pro. Door-mounted is the DIY favorite; wall and glass installs get more involved fast.
| Mount type | Best for | Difficulty | Watch out for |
|---|---|---|---|
| Door-mounted | Wood, steel, or fiberglass exterior doors | Easy – a jigsaw, a drill, a level | Steel/insulated doors need a metal-cutting blade; keep the frame away from the lockset |
| Wall-mounted | Homes where no door faces the yard | Hard – a tunnel kit, stud & wiring awareness | Never cut where electrical or plumbing runs; check for load-bearing framing |
| Sliding-glass panel | Renters, patio doors, no-cut installs | Very easy – drops into the track | Measure track height exactly; some reduce your door’s locking travel |
| Screen-mounted | Seasonal, screened porches | Easy | Lightweight only; a frame kit keeps the flap from tearing the mesh |
Tip: A sliding-glass insert panel (brands like PetSafe and Ideal Pet Products make good ones) is the move for renters — it’s completely reversible and needs zero cutting. Pair it with a secondary door lock since the insert can shorten your slider’s original latch throw.
Flaps, seals, and surviving winter
The flap is what separates a $30 impulse buy from a door that actually holds heat. Single-flap models are cheaper and fine for mild climates or interior use. Dual-flap models trap an air pocket between two panels — that’s your insulation, and it matters everywhere the temperature swings. Look for magnetic closures along the bottom and sides, and a full-perimeter weatherstrip gasket that seals the frame to your door.
If your existing door is drafty to begin with, address that separately with fresh weatherstripping and thresholds — a great pet door can’t fix a bad seal around the door itself. And whatever you install, run a bead of quality exterior caulk around the frame to lock out water and wind.
- Rigid vs. soft flap: rigid panels seal tighter and resist wind; soft vinyl is quieter and gentler for timid pets.
- Magnet strength: strong magnets seal better but can spook small or elderly animals — some doors let you remove magnets to train.
- Frame material: aluminum frames outlast plastic in sun and cold; plastic is lighter and cheaper.
- Locking cover: a slide-in security panel lets you close the door completely when you leave town.
Electronic doors: keeping the wrong critters out
A plain flap is an open invitation — to the neighbor’s cat, to raccoons, to a determined possum. Electronic pet doors solve this by staying locked until they read your pet. Two systems dominate: collar-key doors that unlock for an RFID tag or magnet on your pet’s collar, and microchip doors that read the chip your vet already implanted — no collar accessory to lose.
Microchip models (SureFlap is the best-known) are the gold standard for multi-cat homes and anywhere strays are a problem, because the “key” can’t fall off. They’re battery-powered, so keep spare batteries on hand and note that cold weather drains them faster. If you want basic exclusion without the electronics, even a simple magnetic-latch door blocks most wildlife better than an open flap.
Security, and the honest trade-off
Yes, a pet door is a hole in your security envelope — there’s no getting around it. You minimize the risk with smart placement (not within arm’s reach of the door’s deadbolt), a sturdy locking cover, and by choosing the smallest opening your pet actually needs. For added peace of mind, tie it into your broader home security setup and make sure the host door still carries a solid deadbolt. Electronic doors help here too: many lock automatically and only open for a recognized pet, closing the “prop it open” vulnerability of a plain flap.
Pick by household
RENTER OR PATIO
A sliding-glass insert panel. No cutting, fully reversible, and you take it with you when the lease ends. Add a secondary lock for the shortened latch.
COLD-CLIMATE DOG OWNER
A dual-flap, aluminum-framed, door-mounted model with strong magnets and a locking cover. Weatherstrip and caulk the frame for a true winter seal.
STRAYS & WILDLIFE NEARBY
A microchip electronic door. It reads your pet’s existing chip, stays locked otherwise, and keeps raccoons and the neighbor’s cat outside where they belong.
Shop the whole project
Everything for a clean, weather-tight install
From the door itself to the seal-it-up supplies, stocked from authorized manufacturer channels — the trusted brands your neighborhood store carries. See our guarantee.
Frequently asked questions
What size pet door do I need?
Measure your pet’s shoulder width and their height at the shoulder. The flap opening should be a little wider than the shoulders and at least as tall as the pet standing. When you’re between sizes, choose the larger one, and size for a puppy’s adult dimensions.
Can I install a pet door in a steel or insulated door?
Yes, but you’ll need a metal-cutting jigsaw blade and a bit more patience than with a wood door. Many kits are rated for metal and insulated doors; just confirm the door’s core allows a clean cut and keep the opening clear of the lockset and hinges.
Are pet doors a security risk?
They add a small opening, so placement matters. Keep the door out of arm’s reach of the deadbolt, choose the smallest size your pet needs, and use a locking cover when you’re away. Electronic doors that stay locked until they read your pet reduce the risk further.
How do electronic pet doors work?
They stay locked and only open when they detect an authorized pet. Collar-key models read an RFID tag or magnet on the collar; microchip models read the chip your vet implanted, so there’s no accessory to lose. Both run on batteries you’ll replace periodically.
Will a pet door make my house cold and drafty?
Not if you choose well. A dual-flap model traps an insulating air pocket, and magnetic closures plus a full-perimeter weatherstrip seal keep drafts out. Caulking the frame during installation and using a locking cover in extreme weather seal the deal.
A pet door is a small cut with a big payoff — measure twice, seal it right, and match the flap system to your climate and your critters. For hands-on sizing help or a look at the frames and seals before you cut, your local independent hardware store is the best first stop, or ask us here.
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