A tunnel toy only works if your cat can actually get in, turn around, and come back out without feeling stuck. Before you add one to cart, here's what actually determines whether a tunnel fits — and how to tell if it'll work for more than one cat.

How do I know if a tunnel is the right size for my cat?

Measure your cat around the widest part of their ribcage, then compare that to the tunnel's loop opening — a good fit lets your cat pass through without brushing both sides, and lets them turn around inside instead of having to reverse out. Vets use a similar "lie down and turn around comfortably" standard for carrier sizing, and it works just as well here.

Wrap a soft measuring tape (or a length of string) around your cat's ribcage just behind the front legs — that's typically their widest point, wider than their hips for most cats. A domestic shorthair usually measures somewhere in the 12-16 inch range around the chest, while larger or fluffier breeds run bigger. The tunnel's loop diameter should comfortably clear that measurement with a few inches to spare, since cats also want room to arch their back or pause mid-tunnel to peek out a window. Veterinarian Jenny, DVM, who advises on carrier fit for Petco, recommends checking that a cat can "comfortably lay down and turn around" in an enclosed space — the same logic applies to a tunnel. If your cat has to squeeze, or can only walk straight through without turning around, it's worth sizing up.

Can two cats share one tunnel?

Yes, especially with a spiral or multi-loop design — tunnels with more than one opening give cats room to pass each other or duck into a different loop instead of meeting nose-to-nose in a dead end. PetSmart's pet care team notes that tunnels "can become a great place for chases and interactive play" in multi-cat households.

A single straight tube works fine for one cat at a time, but it can turn into a pinch point when a second cat wants in — someone has to back out. Tunnels built with multiple connected loops or curves, rather than one straight run, solve this naturally by giving cats more than one way in and out, so a game of chase doesn't end in a standoff. If your cats are close in size, look for a tunnel with at least two openings. If one cat is noticeably larger, keep an eye on the first few play sessions to make sure the smaller cat still has an easy way to duck out if things get boisterous.

What if my cat is still growing?

Soft, flexible-frame tunnels are naturally more forgiving than rigid plastic ones — because the fabric gives slightly, a tunnel that's roomy for a kitten usually still works once they're full grown, as long as the frame holds its shape well enough not to collapse under extra weight.

Rigid tunnels with hard plastic or fixed hoops fit however they're built and don't adjust. Soft fabric tunnels with a flexible internal frame have more give — the material flexes slightly around a bigger cat the way it wouldn't around a hard shell. That said, flexible shouldn't mean flimsy: look for a frame that springs back into its full loop shape after each use rather than one that stays dented or flattened, since a collapsed loop is a lot harder for a growing cat to push through. If you're buying for a kitten and want the tunnel to last into adulthood, size up slightly rather than down, and check the material description for a supportive internal frame.

Are collapsible fabric tunnels safe to leave out unsupervised?

Most are fine once you've watched your cat use it a few times, but pet care guides recommend supervising the first several play sessions and choosing tunnels made from durable, non-fraying material so there's nothing loose for a cat to chew off and swallow.

PetSmart's pet care team recommends supervising a cat's first sessions with any new tunnel "in case there's a risk of getting tangled in toys or in a poorly designed tunnel," and choosing "non-toxic, durable materials that won't easily tear or fray" so there's no loose fabric or trim for a cat to chew and ingest. Once you've seen your cat move through the tunnel comfortably a few times — entering, turning around, and exiting without getting stuck — most owners feel comfortable leaving it out as a regular fixture. Check stitching and any hanging toys periodically for wear, especially if your cat is an enthusiastic chewer.

FAQ

Do I need to measure my cat every time I buy a new toy size?

Not usually. Once you know roughly where your cat falls — their chest measurement — you can reuse that number for tunnels, carriers, and other enclosed toys, since the "comfortably turn around" standard stays about the same across products.

Is a longer tunnel automatically better?

Not necessarily. A longer tunnel gives more room to explore, but a shorter one with a wider loop is often more welcoming for cats who are new to tunnels, since they can see both ends and don't feel committed to a long, dark passage.

My cat sniffed the tunnel and walked away — did I get the wrong size?

Probably not a sizing issue. Cats often need a few days to investigate something new at their own pace. Placing a treat or a bit of catnip just inside the opening usually does more to encourage first use than a resize would.

Our Pick: The ZEZE Wiggle & Play Tunnel Collection

ZEZE Forest Snake Catnip Tunnel Spiral Cat Toy with Bell & Hanging Teasers is built as a multi-loop spiral, not a single straight tube — exactly the shape that gives cats room to turn around and pass each other instead of backing out. Catnip is tucked inside the snake's head, a bell adds sound, and hanging teasers on both ends keep play going once your cat's inside. The flexible frame holds its coiled shape through active play and folds flat for storage when you're done.

For a tighter, more contained spiral, ZEZE Monica Spring Catnip Crinkle Feather & Bell Collapsible Spiral Tube Tunnel Cat Toy pairs catnip and crinkle paper at both ends with a fork-shaped hanging toy, a jingling bell, and a feather tip at the entrance. Its 360-degree spiral opening gives cats plenty of room to dash through and turn around, and the spring-loaded frame collapses flat in seconds for travel or storage.

Sources: PetSmart Learning Center, "The Ins and Outs of Cat Tunnels"; Petco Vet Q&A, Jenny DVM, "How to measure your cat for the perfect carrier size and fit"