Cat doors
Cat Doors Sized for the Cat You Actually Have
Cat doors are sized around a drill template. Here is how to size one around your cat, and the option renters never hear about.
By Joel Wood. Picks and specs last checked .
The complaint
“He squeezes through it sideways. It took a month to get him to use it at all, and now the neighbor’s cat comes in and eats his food.”
Cat doors are sold by the size of the hole you have to cut, not by the size of the cat. That’s backwards, and it’s why so many large cats end up squeezing through an opening that was designed around a drill template.
There’s also a version of this problem nobody sells a solution for: you rent, and you’re not cutting a hole in anything.
Why it fails
- The flap is sized to the tool, not the animal. A 6-inch flap fits the hole saw. It doesn’t fit a 9-inch-wide cat.
- The sill sits on the floor. Installation instructions put the door at the bottom of the panel because that’s where the template goes. Cats step through openings at chest height; a floor-level flap makes them duck and climb.
- The clever door has a battery. Microchip readers keep the neighbor’s cat out until the batteries die, and then the door does whatever its designers decided a dead door should do. Few listings say which.
- Renters get nothing. Every mainstream product assumes you own the door.
On weather
A single flap is a draft. In a wet or cold climate, look for a dual flap or a magnetic seal, and check whether the magnet is strong enough that your cat can still push through it. The two requirements pull against each other and manufacturers rarely say which way they’ve resolved it.
What to look for
Check every one before you buy. This is the part the pin couldn't fit.
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Measure your cat's shoulders, then add 2 inches
Shoulder width at the widest point is the number that matters. Most standard flaps run about 6 to 7 inches wide, which is fine for an average cat and too narrow for a Maine Coon or a large Ragdoll. Those often need 9 inches or more. A cat that has to compress to get through will start using the door less, then stop.
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The flap bottom should sit at the cat's belly, not on the floor
Cats step through a cat door. They don't crawl. If the opening starts at floor level they have to duck and climb, which is awkward enough that older or stiffer cats give up on it. Measure floor to the bottom of the chest and set the flap sill just below that.
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Check the battery before you buy the feature
Microchip and collar-tag doors solve a real problem, the neighborhood cat helping itself to your kitchen. They also die. Find out what battery it takes, what the claimed life is, and whether it fails open or locked when flat. A door that locks your cat out at 2 a.m. is a different product than the one you thought you bought.
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A four-way lock
In only, out only, both, neither. You will want "in only" the evening before a vet appointment, and you'll want it badly.
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If you rent, a window insert or a door panel, not a hole
Sash inserts and panels that replace a single pane give you a cat door with no cutting and no patching. They come out when you leave. This is the option almost nobody knows exists, and it's the difference between having a cat door and not.
Is a microchip cat door worth it?
Yes if another animal is coming in; no if your only problem is the weather. A microchip door reads your cat's existing chip and stays locked for everyone else. The trade-offs are batteries, a click that some cats dislike, and an opening that is often smaller than a plain flap. Check the fail state, because most makers don't say what the lock does when the battery dies.
Is there a renter-friendly cat door?
Yes, two kinds that need no cutting. A window sash insert sits in the track like an air conditioner panel, and a sliding-glass door panel springs into the slider track. Both lift out when you move. The catch is that your window or slider can no longer reach its own latch, so budget for a dowel or a clamp-on lock.
The fixes
Products that pass, and where each one falls short
Every card below lists the product's known flaw. If we can't name one, we don't list it.
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Large Cat Flap 221
Cat Mate · Under $100
- The opening is about 7 inches wide, close to an inch more than most standard flaps.
- A four-way lock and a three-year guarantee for around $20 to $30.
- Lines itself through doors and walls up to 2 inches thick, so most installs need no separate tunnel.
Known flaw
Seven inches is big for a cat door and still short of the 9 inches a broad Maine Coon needs. Nothing sold as a cat door gets there. Cat Mate only publishes the cut-out size, so the opening figure comes from retailers. Owners say the lock tabs are stiff to move, and some report the lock breaking early.
Link to Cat Mate coming soon
SureFlap Microchip Pet Door
Sure Petcare · $100–250
- The widest opening we found on a microchip door, about 7 inches across. The company's standard Microchip Cat Flap is 5 5/8 inches, which rules out most big cats.
- Reads 9, 10 and 15-digit chips, which matters in the US where older chip formats are still common, and remembers up to 32 pets.
- The manual tells you to set the tunnel base at your pet's stomach height, which most doors never mention.
Known flaw
Sure Petcare doesn't publish what the lock does when the batteries die, and owner accounts disagree, so treat the low-battery light as a deadline. It runs on four C cells rated for at least six months. Raccoon resistance gets mixed reviews: the manual has a custom mode for animals that learn to pull the flap outward, and you have to switch it on yourself. The lock clicks loudly enough to put off a timid cat. The published opening width also varies between 7 and 7 1/2 inches depending on which listing you read.
Link to Sure Petcare coming soon
Aluminum Sash Window Pet Door
Ideal Pet Products · $100–250
- No cutting and no tools. It sits in a sash window track and lifts out when you move.
- The Chubby Kat flap is 7 1/2 by 10 1/2 inches and keeps the four-way lock. The extra large flap is 10 1/2 inches wide, the only option here that clears 9.
- Three widths cover windows from 23 to 38 inches.
Known flaw
Drafts are the trade-off. Owners report gaps around the insert and a flap magnet that a gust can push open, so budget for extra weatherstripping. A few cats have flipped the lock lever and shut a housemate outside. With the insert in, the sash can't reach its own latch, so plan on a dowel or a sash lock. The dog-sized flaps lose the four-way lock, and the door sits at sill height, so some cats will need a step.
Link to Ideal Pet Products coming soon
1-Piece Sliding Glass Pet Door
PetSafe · $100–250
- PetSafe publishes the real opening and the step-over. The medium flap is 8 1/4 by 12 3/16 inches with a 1 3/4 inch step, and the large is 10 1/4 inches wide.
- Spring-loaded into the slider track, so it goes in without cutting and lifts out when you leave.
Known flaw
It's a single pane of glass with a flap in it, and owners in cold climates report real heat loss even after adding their own weatherstripping. Some also say the flap blows open in wind. Your slider's own lock won't reach any more, so you either screw on the included latch, which leaves holes a landlord will see, or drop a bar in the track. There's no four-way lock, only a slide-in closing panel.
Link to PetSafe coming soon
Get the cat door sizing card
The measurement to take, the flap height most doors get wrong, and the renter option. We'll also email you when something in this category actually passes, which isn't often.