Buying guide
What Size Cat Carrier Do I Need? Sizing + Airline Limits
What size cat carrier do I need? Measure nose to tail base, standing height, and width, then compare the inside with four US airlines' cabin limits.
Editorial buying guide · Updated · ByPet Product Compass Editorial ·Editorial policy ·Methodology
What size cat carrier do I need? Choose a carrier whose inside length covers the cat from the tip of the nose to the base of the tail, with inside height and width for the cat to stand and turn. For a flight, the outside of that carrier also has to fit the airline under-seat limit in the table below.
Petmate’s cat carrier size guide (page date September 28, 2026) is the measuring method: nose to the base of the tail, standing height, and shoulder width, compared with the usable interior and the doorway. The airline numbers were read on each airline’s page on October 31, 2026. Check the current pet fee on the airline page.
Airline in-cabin cat carrier limits
Soft-sided and hard-sided limits differ on United and American. Delta prints a recommended soft-sided maximum and does not print a separate hard-sided maximum. JetBlue prints one maximum for both. Alaska’s pet pages and Southwest’s carrier article did not return dimensions in the copies opened today, so those airlines are not in this table.
| Airline | Soft-sided | Hard-sided | Exceptions | Short quote | Source, checked October 31, 2026 |
|---|---|---|---|---|---|
| United | 11 x 18 x 11 in | 9 x 17.5 x 12 in | Boeing 737 MAX: carrier no more than 10 inches tall. One pet per person on the A319, A320, A321neo, 737-800, 737-8 (MAX 8), 737-900, and 737-9 (MAX 9). | “The maximum size of a soft-sided pet carrier can be 11 in x 18 in x 11 in.” Hard-sided: “9 in x 17.5 in x 12 in.” | United pets |
| American | 18 x 11 x 11 in (length x width x height), all flights | Mainline 19 x 13 x 9 in. American Eagle 16 x 12 x 8 in. | Soft-sided kennels need nylon mesh ventilation on 3 or more sides. Airbus A321T (3 cabin), Premium Cabin row only: pet and carrier together must not exceed 20 lb (9.07 kg); First has no under-seat stowage, so carriers go in a front compartment. | “18 x 11 x 11 inches” for soft-sided carriers on all flights. | American pets |
| Delta | Recommended maximum 18 x 11 x 11 in | Not stated on the page | Under-seat space varies by aircraft. Ventilation openings on 3 sides for domestic travel and 4 sides for international travel. The kennel must fit fully underneath the seat. | “Delta recommends a soft-sided kennel with maximum dimensions of 18” x 11” x 11” since this fits most aircraft types.” | Delta pet travel |
| JetBlue | 17 in long x 12.5 in wide x 8.5 in high | Same limit. The page accepts soft-sided and hard-sided carriers. | The pet must be able to stand up and move around inside the carrier. The carrier needs a leak-proof bottom. One pet per carrier. | “Carriers cannot exceed 17" L x 12.5" W x 8.5" H.” | JetBlue pets |
United prints the three numbers and does not label which one is length, width, or height. The 737 MAX sentence is the line that says “tall.” American’s table header says length + width + height. JetBlue labels length, width, and height. Delta does not label the three sides.
Petmate’s air-travel section says: “Do not rely on a universal under-seat measurement because aircraft configurations can differ.”
What size cat carrier do I need: three measurements
Measure the cat. Petmate says to measure from the tip of the nose to the base of the tail, and not to include the full tail. Measure standing height from the floor to the top of the head, and account for the ears if they stand up. Measure across the widest part of the shoulders or rib cage, then check the doorway as well as the interior width.
Choose the inside. Compare those three numbers with the usable interior. Petmate’s fit questions are whether the cat can stand without a sustained crouch, turn around, lie down, and enter the door without being squeezed. Walls, a raised floor, and a liner reduce that space. If you add padding, measure the space that is left.
Compare the outside with the airline limit. The exterior is the figure in the table above. Petmate says exterior measurements help you decide whether the carrier fits in a vehicle or under an airline seat, and that they do not tell you how much room the cat has inside.
Coastal Pet’s airline page uses a different tape: collar to tail for length, shoulder to shoulder for width, and paw to the tip of the ears while laying down for height, then add 2-3 inches. Those starting points are not Petmate’s nose, floor, and shoulders. Keep the two methods separate.
Vet and car trips versus flights
| Vet or car trip | Flight in the cabin | |
|---|---|---|
| What limits apply | The carrier’s own size line and the space in the car. The airline table does not apply. | The airline’s outside limit for that soft-sided or hard-sided carrier, on that aircraft, plus the interior fit. |
| What to measure | Nose to tail base, standing height, shoulder width, the interior, and the doorway. | The same interior measurements, then the carrier’s exterior against the airline table. |
On a drive, the airline box is not the limit. The interior still has to let the cat stand, turn, and lie down, and the outside only has to fit the car and sit level.
An 18-inch cat checked against the airline limits
These rows are arithmetic for an example cat, not a measured animal and not a product. Nose to tail base: 18 in. Standing height: 10 in. Shoulder width: 6 in. The interior target, using Petmate’s method, is at least those three numbers, with room to stand, turn, and lie down. Petmate does not publish a fixed number of extra inches.
The airline figure is the outside of the carrier. An outside length of 18 in cannot hold an inside length of 18 in.
| Limit | Outside maximum | Against this example |
|---|---|---|
| United soft-sided | 11 x 18 x 11 in | Longest side is 18 in, the same as the cat’s length, so the inside is shorter than 18 in. |
| United hard-sided | 9 x 17.5 x 12 in | Longest side is 17.5 in, which is shorter than 18 in. |
| United, Boeing 737 MAX | Height no more than 10 in | Equal to the 10 in standing height, so a 10 in outside height leaves no interior headroom above that height. |
| American soft-sided, all flights | 18 x 11 x 11 in (length x width x height) | Outside length equals the cat’s length. Outside height is 11 in. |
| American hard-sided, Mainline | 19 x 13 x 9 in (length x width x height) | Outside length is 1 in longer than the cat. Outside height is 9 in, which is under the 10 in standing height. |
| American hard-sided, Eagle | 16 x 12 x 8 in (length x width x height) | Length and height are both under the example cat. |
| Delta recommended soft-sided | 18 x 11 x 11 in | Longest side equals the cat’s length. The page states no hard-sided maximum. |
| JetBlue, soft-sided or hard-sided | 17 in long x 12.5 in wide x 8.5 in high | Length and height are both under the example cat. |
A shoulder width of 6 in is under every width in the table. Length and height are the stops for this example. A shorter cat is a different row: measure that cat and repeat the three steps.
Carriers with published dimensions
Three carriers have published exteriors in the records used here. Airline rules decide; check your airline. Check current price on Amazon. Interior size was not in the Coastal or Gardner records, so this table does not say the cat fits inside.
| Carrier | Exterior as stated | Max pet weight as stated | Type | Trip fit vs the limits above |
|---|---|---|---|---|
| Bergan Comfort Carrier Small, ASIN B00XHFU1TK | Brand page: 16 in L x 8 in W x 11 in H. Amazon item-dimension table: 12 in L x 16.25 in W x 8 in H. The listing states this two different ways; check the product page. | Not stated. The carrier’s own item weight is 1.8 lb. | Soft-sided | The brand’s 11 in side equals the 11 in side on the United, American, and Delta soft figures, and it is over JetBlue’s 8.5 in height and over United’s 10 in 737 MAX height cap. The table’s 16.25 in side is over American’s 11 in soft width and JetBlue’s 12.5 in width. |
| Gardner Pet Expandable, ASIN B0GXK8PVQ8 | Model name 18x12x12. Main compartment 18.1 x 11.8 x 11.8 in. Expanded 28.4 x 18.1 x 11.8 in. | Up to 15 lb. The listing says best for pets under 16 in long and 10 in tall. | Soft-sided, expandable | 11.8 in is over the 11 in soft-carrier figure United, American, and Delta print. 18.1 in is over American’s 18 in length and over the 18 in side United and Delta print. It is also over JetBlue’s 17 in length and 8.5 in height. The expanded size is larger. The listing title uses an approval phrase. Airline rules decide; check your airline. |
| Gardner Pet Large Expandable, ASIN B0H2F16GDB | 20.5 x 13.4 x 13.4 in. Expanded 20.5 x 38.2 x 13.4 in. | The listing states this two different ways; check the product page. The listing also says best for pets under 18.5 in long and 12 in tall. | Soft-sided, expandable | Larger on every side than the in-cabin limits above. Car and vet trips, not the cabin. |
The Gardner expandable listing also says the carrier folds to about 2.75 in and the shoulder strap runs 30 to 50.8 in.
The Bergan brand page lists a fleece bed and a seat-belt loop on the Comfort Carrier. That is a feature list. It is not a cabin assignment.
If the cat stays home and you are setting the feeding plan for while you are away, use how to choose an automatic cat feeder and the PETKIT format shortlist.
Product-selection path
Products referenced in this guide
A car or vet trip when you can confirm which exterior measurement is current and the inside still lets your cat stand and turn
- Best for
- A car or vet trip when you can confirm which exterior measurement is current and the inside still lets your cat stand and turn
- Before buying
- Confirm the current listing details.
Skip if: You need a published interior size, a published pet weight limit, or an outside shape that is already inside every airline limit you might fly.
What to verify before buying
Product listings can change. Check the exact variant, size, ingredient or material information, directions, warnings, seller, return terms and current availability before buying.
Last checked: 2026-10-31. This page does not present hands-on product testing.
A car or vet trip for a pet the listing describes as under 16 in long, under 10 in tall, and up to 15 lb, when you do not need the main compartment to sit inside an 11 in soft-carrier limit
- Best for
- A car or vet trip for a pet the listing describes as under 16 in long, under 10 in tall, and up to 15 lb, when you do not need the main compartment to sit inside an 11 in soft-carrier limit
- Before buying
- Confirm the current listing details.
Skip if: The trip is in the cabin and the airline's soft-carrier figure is 11 in on the short sides, or you need a published interior measurement.
What to verify before buying
Product listings can change. Check the exact variant, size, ingredient or material information, directions, warnings, seller, return terms and current availability before buying.
Last checked: 2026-10-31. This page does not present hands-on product testing.
- Source: Amazon product listing (ASIN B0GXK8PVQ8)
Car and vet trips for a pet the listing describes as under 18.5 in long and 12 in tall, when the carrier does not need to fit under an airline seat
- Best for
- Car and vet trips for a pet the listing describes as under 18.5 in long and 12 in tall, when the carrier does not need to fit under an airline seat
- Before buying
- Confirm the current listing details.
Skip if: The trip is in the cabin, or you need one clear pet weight limit and a published interior size.
What to verify before buying
Product listings can change. Check the exact variant, size, ingredient or material information, directions, warnings, seller, return terms and current availability before buying.
Last checked: 2026-10-31. This page does not present hands-on product testing.
- Source: Amazon product listing (ASIN B0H2F16GDB)
Sources
FAQ
What size cat carrier do I need if my cat is 18 inches from nose to tail base?
Petmate's method says the interior has to cover that nose-to-tail-base length so the cat can turn and lie down, and the cat also has to be able to stand. Petmate does not publish a multiplier. An airline limit is the outside of the carrier, so an 18 in outside length is already shorter than an 18 in interior. Use the worked example on this page against each airline row.
Do soft-sided and hard-sided cat carriers share one in-cabin size?
Not on the pages read October 31, 2026. United prints 11 x 18 x 11 in for soft-sided and 9 x 17.5 x 12 in for hard-sided. American prints 18 x 11 x 11 in for soft-sided on all flights, 19 x 13 x 9 in for hard-sided on Mainline, and 16 x 12 x 8 in for hard-sided on American Eagle. JetBlue prints one maximum, 17 x 12.5 x 8.5 in, for both. Delta recommends 18 x 11 x 11 in for a soft-sided kennel and does not print a hard-sided maximum.
Should I size a cat carrier by the inside or the outside?
Use the inside for the cat and the outside for the airline or the car. Petmate says to compare nose-to-tail-base length, standing height, and shoulder width with the usable interior and the doorway. Exterior measurements tell you whether the shell fits under a seat or in a vehicle.
If a listing says the carrier is made for airlines, does that set the size?
No. Airline rules decide; check your airline. United, American, Delta, and JetBlue each print their own limits, and those limits are not the same number. A phrase on a product title does not replace that table.
What size cat carrier do I need for a vet visit in the car?
The airline under-seat table does not apply. Measure nose to tail base, standing height, and shoulder width, and compare them with the interior and the doorway. The outside only has to fit the car and stay level.