We're building a tunnel to allow our cat to enter / exit a master suit (bedroom + bathroom) when the door's closed. How should I think about the right size to allow the cat to go through the tunnel comfortably? The tunnel isn't very long but it's long enough that the cat will have to walk several steps through the tunnel (it's not a step through), and navigate a 90 degree turn.

She's very small for an adult cat - but we might get bigger cats later, so this should be sized for any average cat (maybe not the largest of Maine Coons).


3 Answers 3


The most popular cat tunnel on amazon has a 9.5 inch diameter. Cat doors on amazon seem to all be in the 7-9 inch range as well.

I have a 15 pound cat, and got her an 11 inch diameter tunnel. She can navigate that just fine, so you probably won't have to go over 11 inches, even for a very large cat.


There are a lot of variables when choosing a tunnel. Concrete forms in 8,10 & 12 inches sizes can be found at your local DIY store for around $5. Buy one of each and bring it home for a trial. We use them a lot with Rabbits but they work good for cats also.

They are easy to get, returns are easy, and if you like them they are inexpensive to own and replace. They last well and even with heavy usage they last years.


A determined cat can get through just about any space they can get their head through.

I'd suggest wandering out to a large pet store and seeing what size they make the openings/tubes on various kitty condos, or websearching that. Or websearching videos of cats getting through/into small things, though you can lose a week to that once you start.

Why tunnel? Why not the standard cat-flap approaches?

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