Airline pet carrier size checker

In-cabin pet carrier size limits by airline

These are the maximum carrier sizes each airline publishes for a pet under the seat, copied from the airline's own website in October 2026. We only list airlines whose current limits we could confirm on their official pages; American and United are missing because we couldn't load their pet pages when we checked, not because they don't take pets.

• Air Canada: Soft-sided, flexible carriers only since June 1, 2025. The pet must be able to stand up, turn around and lie down.
• Alaska Airlines: Soft-sided carriers only; hard-sided kennels are not allowed in the cabin. The carrier counts toward your carry-on allowance.
• Delta Air Lines: The real maximum depends on the under-seat space of your aircraft. Delta recommends a soft-sided kennel of up to 18 × 11 × 11 in.
• Frontier Airlines: The container must let the pet stand, turn around and lie down, and fit under the seat in front of you.
• JetBlue: Soft-sided and hard-sided carriers are accepted. The pet must be able to stand up and move around with ease.
• Southwest Airlines: Southwest recommends soft-sided carriers because under-seat space varies by seat. Its own branded carrier is 15 × 10 × 10 in.
• WestJet: Soft-sided, airline-approved kennels only. The kennel counts as your personal item.

How do you measure a pet carrier?

Measure the outside, not the inside, because that is what has to slide under the seat. Include side pockets, frames and any handle or wheel that doesn't fold away. Measure the height with the carrier zipped and standing on the floor, the way it will sit under the seat.

The checker lets you turn the carrier on the floor, so length and width can swap, but it won't tip it on its side: your dog has to stay upright. Soft carriers give a little, and WestJet notes you may need to adjust a soft kennel to the height and depth under the seat, but there is no published allowance for squashing, so a carrier over the limit is a risk at the gate.

Is there one carrier that fits every airline?

Among the airlines in this checker, as of October 2026:

• Soft-sided: a carrier up to 16 × 10 × 8 in (41 × 25 × 20 cm) fits every listed limit. The tightest numbers in the table set it.
• Hard-sided: only Frontier Airlines, JetBlue and Southwest Airlines accept them, and a carrier up to 17 × 10.5 × 8 in (43 × 27 × 20 cm) fits all three.

Height is the limit most carriers fail. Several airlines cap it at 8 to 8.5 inches, so a carrier that is generous in length can still be refused because it is an inch too tall.

How big can my dog be to fly in the cabin?

The airlines here set their limit by the carrier, and the dog has to fit inside it comfortably. Frontier, JetBlue, Southwest and Air Canada all say the pet must be able to stand up and turn around, and Air Canada adds that a pet can be refused travel if its carrier is too small for it. In practice, that means a dog whose standing height (floor to top of head) is less than the carrier's height. Turn on "Check my dog fits inside" in the checker to test it.

If your dog is too big for any under-seat carrier, read our guide to airlines that allow large dogs in cabins. For a crate that travels in the hold or the car, the crate size calculator works out the size from your dog's measurements.

What to do before you book

• Book your pet's place early. Alaska and WestJet both limit the number of pets per flight, and Alaska takes reservations first come, first served.
• Get your dog used to the carrier before travel day, as Alaska advises.
• Ask your vet before giving any sedative. Alaska and Frontier both point out that the effects of tranquilizers at altitude are unpredictable.
• Check entry rules for international trips: the pet travel requirements by country tool and the dog travel checklist cover paperwork and packing.