A “TSA approved” cat carrier doesn’t have one universal size, because TSA focuses more on safe screening access than exact measurements. In real-world travel, the size that matters most is your airline’s under-seat carry-on limit—since most cats fly in-cabin in a soft-sided carrier that fits beneath the seat.
As a practical guideline, many pet parents choose a soft-sided cat carrier around 18″ long x 11″ wide x 11″ high (or smaller) because that range often fits under typical airplane seats. Some airlines allow slightly larger dimensions (for example, up to about 19″–20″ long), while others are stricter—especially on height. Always confirm the exact measurements for your specific flight and seat type before you buy.
To keep your cat comfortable and secure, look for a carrier with flexible sides, breathable mesh panels, a sturdy base, and secure zippers. A removable, washable pad is a nice bonus for long days of travel.
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Measure your cat: nose to base of tail (length) and floor to top of shoulders (height). Choose a carrier that lets them turn around and lie down.
Measure your seat space: under-seat height is often the tightest dimension.
Plan for screening: TSA typically has you remove your cat from the carrier at the checkpoint, so easy-access openings and secure closures help reduce stress.
It depends on the airline and the aircraft, but most in-cabin carriers must fit under the seat, commonly landing around 18″ x 11″ x 11″ or similar. Check your airline’s current pet policy for exact limits.
Southwest generally requires pets to travel in an approved carrier that fits under the seat, which limits travel to small dogs that can comfortably stand and turn around inside. Always verify the latest carrier size rules and pet restrictions directly with the airline before booking.
