Quick answer: United takes a cat or dog in the cabin for $150 each way, in a soft-sided carrier up to 18 x 11 x 11 inches or a hard-sided one up to 17.5 x 12 x 9 inches. On a Boeing 737 MAX, though, no carrier can be taller than 10 inches.
That last rule is the one most carriers miss, so the picks below show how each one measures against both limits.
At a glance
Picking a carrier for United looks easy until you notice that the plane matters. The same bag that slides under a seat on an Airbus can be an inch too tall on a Boeing 737 MAX.
So I read United’s pet pages and its contract of carriage line by line, then held four popular carriers up against the numbers. Here’s what fits, what nearly fits and what to measure before you fly.
What United says about carriers
Everything in this section comes from United’s traveling with pets page and its contract of carriage, which United revised on 30 September 2026. I read both on 21 October.
- Soft-sided: up to 18 inches long, 11 wide and 11 high (45 x 27 x 27 cm).
- Hard-sided: up to 17.5 inches long, 12 wide and 9 high (44 x 30 x 22 cm).
- Boeing 737 MAX: no carrier taller than 10 inches, soft or hard.
- Fee: $150 each way, and the carrier doesn’t count as your carry-on or personal item.
- Weight: no limit and no breed limit, as long as your pet stays comfortably inside.
- One pet per carrier, and the carrier stays closed under the seat in front of you the whole flight.
Some older guides give United’s hard-sided height as 7.5 inches. United’s own pages say 9 inches, so that’s the number I used.
The 737 MAX rule, and why it matters
Three of the four carriers below are taller than 10 inches, because they’re built to the 11-inch soft-sided height United itself allows. Its contract adds one exception: on a Boeing 737 MAX, no carrier can be taller than 10 inches.
Check the aircraft type for each flight before you choose a carrier. If you’re flying a MAX, go for a carrier 10 inches tall or less, or one with a soft frame that genuinely compresses without squashing your pet.
The carriers, side by side
The sizes and weight limits below come from each Amazon listing, which is the seller’s claim, and I checked prices and stock on 21 October 2026. I haven’t measured any of them, so please do that when yours arrives.
| Carrier | Outer size | Pet weight | Under the 737 MAX cap? | Price |
|---|---|---|---|---|
| Petsfit Small Double Expandable Carrier | 16 x 10 x 9 in | Up to 9 lb | Yes | $47.49 |
| Petsfit Medium Expandable Carrier | 17 x 11 x 11 in | Up to 13 lb | No, 1 in over | $53.17 |
| Sherpa Original Deluxe, Medium | 17 x 11 x 10.5 in | Up to 16 lb | No, 0.5 in over | $59.99 |
| Lekereise Top-Expandable Pet Carrier | 18 x 11 x 11 in | Up to 15 lb | No, 1 in over | $21.99 |
Petsfit Small Double Expandable Carrier
Clears the 737 MAX cap
Best for: a cat or very small dog up to 9 lb, especially on a Boeing 737 MAX.
Inside United’s limit with room to spare, and 1 inch under the 10 in height cap on a 737 MAX.
Up to 9 lb (carrier about 2.6 lb) · 16 x 10 x 9 in · $47.49 on Amazon, 21 October 2026
Full details
The listing gives 16 x 10 x 9 inches and pets up to 9 lb, and says this size is small, so choose by your pet’s weight and length. Petsfit’s own page for this family mentions pets up to 15 lb, which doesn’t match, so I’d stick with 9 lb.
The two side panels unzip to 23.5 x 16 inches for layovers, but they have to stay zipped under the seat.
Sold by Petsfit on 21 October 2026. Sizes and weight limits are the seller’s claims.
Petsfit Medium Expandable Carrier
The brand names United
Best for: a cat or small dog up to 13 lb on United’s Airbus and other non-MAX jets.
Inside United’s soft-sided limit, but 1 inch over the 10 in height cap on a 737 MAX.
Up to 13 lb (carrier 2.5 lb) · 17 x 11 x 11 in · $53.17 on Amazon, 21 October 2026
Full details
Petsfit’s own page says its S and M sizes are approved for Delta, United and American, which makes this the only carrier here whose brand names United. That’s a brand claim, not United’s approval.
The Amazon listing gives 17 x 11 x 11 inches in its headline, 17.99 x 10.98 x 10.98 in its details, and mentions Delta rather than United. One side panel expands to 20 x 17 inches when you’re not under a seat.
Sold by Petsfit on 21 October 2026. Sizes and weight limits are the seller’s claims.
Sherpa Original Deluxe, Medium
Soft frame that flexes
Best for: a dog up to 16 lb, and a traveller who wants a classic soft-sided tote.
Inside United’s soft-sided limit; on paper half an inch over the 737 MAX cap, though the frame compresses.
Up to 16 lb (carrier 3 lb) · 17 x 11 x 10.5 in · $59.99 on Amazon, 21 October 2026
Full details
Sherpa’s size table lists the Medium at 17 x 11 x 10.5 inches, for pets up to 16 lb, 16 inches long and 9.5 inches tall. Sherpa says the spring wire frame lets the back push down several inches to fit under seats, which is a brand claim.
Stock is thin: on 21 October the Medium in black was sold out on Sherpa’s site, and Amazon showed one left from a third-party seller, so check before you count on it.
Sold by Express EcoMarket (third-party seller) on 21 October 2026. Sizes and weight limits are the seller’s claims.
Lekereise Top-Expandable Pet Carrier
Right at United’s limit
Best for: a budget pick for a pet up to 15 lb on non-MAX aircraft.
Matches United’s soft-sided limit exactly, and 1 inch over the 737 MAX cap.
Up to 15 lb (carrier 2.78 lb) · 18 x 11 x 11 in · $21.99 on Amazon, 21 October 2026
Full details
The listing names Delta, United and American in its title and suggests checking the size with your airline. It lists room for a pet up to 17 x 10 x 10 inches inside, with mesh on five sides.
The top unzips to add 3.9 inches of height, so keep it closed on the plane. A near twin (ASIN B0G4M3W62D) has mesh on three sides and was listed at $49.99 on the same day.
Sold by Syroad on 21 October 2026. Sizes and weight limits are the seller’s claims.
The ones I left out
The Sherpa Original Deluxe in Large measures 19 x 11.75 x 11.5 inches, longer and taller than United allows, and the Petsfit Large at 19 x 12 x 12 inches is too big as well.
Lekereise’s 18 x 13 x 9.5 inch carrier is too wide, and the SturdiBag Pro in Medium measures 15 x 12 x 11.75 inches. The SturdiBag Small would fit on paper, but I couldn’t find it on Amazon, so it isn’t here.
Where you can sit with your pet
United doesn’t publish under-seat measurements by aircraft. It publishes seat rules instead, and those decide whether your carrier has room.
You can’t sit with a pet in an exit row, a United Premium Plus seat or the front row of any cabin. In Economy on a 757-200 you need a window seat, and on 737-800 and 737-900 family aircraft an aisle or a window.
Each plane also has a cap on pets per cabin, and space goes to whoever reserves it first.
On most flights you can bring two pets if you buy a second seat right next to yours. On the A319, A320, A321neo, 737-800, 737-900, MAX 8 and MAX 9 it’s one pet per person. Some United Express flights don’t take pets at all.
Booking your pet and the day you fly
- Add your pet when you book on united.com by choosing “Travel with a pet” as a traveler, or add it later in My Trips. You can’t add a pet in the United app.
- Flying internationally? You have to call United to add a pet, and dogs must be at least six months old (kittens four months). On domestic flights the minimum is two months.
- Check in at a kiosk for a domestic flight. It prints a special tag for your carrier.
- On board, your pet stays in the closed carrier under the seat in front of you at all times.
Our guide on keeping a dog calm on a flight has ideas for getting your pet used to the carrier in the weeks before.
Where United won’t fly your pet
United publishes a list of states and countries it won’t fly pets to, from or even through, and Hawaii is on it.
If Hawaii is your destination, our guide to getting your dog to Hawaii without quarantine covers the airlines that do fly pets there.
No more PetSafe
United no longer takes pets through its PetSafe cargo program. Pets only fly in cargo for certain active-duty military and State Department moves, and that program now covers reassignments between Guam and Honolulu.
If your dog is too big for the cabin, you’ll need another airline or a pet shipper, and our guide to what it costs to ship a dog compares the options.
Service dogs and emotional support animals
United’s service animal page lets you fly with up to two trained service dogs for free, or one service dog and one pet. Dogs have to be over four months old on domestic flights and six months on international ones.
Its contract asks for the DOT Service Animal Air Transportation Form at least 48 hours before departure, plus a relief form for flights of eight hours or more. Therapy and emotional support animals fly as pets, in a carrier, for the fee.
How I chose these
I read United’s pet pages and its full contract of carriage, then opened every Amazon listing and brand page on 21 October 2026, and wrote down sizes, weight limits, prices, sellers and airline claims exactly as published.
Believe it or not, I’m not a dog, so I can’t tell you how comfy these are from the inside, and I haven’t flown with any of them. What I can do is hold the numbers up against United’s and tell you where they disagree.
I left out customer ratings, because they don’t tell you whether a carrier fits United’s rules. More on how I make my guides.
How to pick one for your pet
Start with your pet: it needs to stand, turn around and lie down without pressing on the sides, and the carrier’s weight rating should cover it with a little to spare.
Then check your aircraft. On a 737 MAX look for 10 inches tall or less, and on every other United jet stay within 18 x 11 x 11 inches for soft-sided or 17.5 x 12 x 9 for hard-sided.
Measure the carrier with everything zipped, and keep any expansion panels closed under the seat. United’s staff make the call at the gate, so a carrier that is clearly inside the limit is worth more than one that only just fits.
Flying other airlines too? Our Delta carrier guide compares the same carriers against Delta’s rules.
Frequently asked questions
What size pet carrier does United allow?
United allows soft-sided carriers up to 18 x 11 x 11 inches and hard-sided ones up to 17.5 x 12 x 9 inches. On a Boeing 737 MAX, any carrier can be no more than 10 inches tall.
How much does United charge for a pet in the cabin?
United charges $150 each way for a cat or dog in the cabin. Its contract of carriage puts it at 150 USD or 150 CAD each way, so $300 for a round trip.
Does the pet carrier count as my carry-on on United?
No. United’s contract of carriage lists a pet carrier among the items that don’t count toward your one carry-on and one personal item, though the pet fee still applies.
Can I bring two pets on United?
On most flights you can bring up to two pets if you buy a second seat next to yours, one pet per carrier. On A319, A320, A321neo, 737-800, 737-900 and MAX 8 and MAX 9 aircraft, it’s one pet per person.
Can I fly my dog to Hawaii on United?
No. Hawaii is on United’s list of places it won’t fly pets to, from or through, along with Australia, New Zealand, the UK and others. Trained service dogs are handled separately.
Is there a weight limit for pets on United?
United doesn’t set a weight limit or breed limit for cabin pets. Your pet just has to fit comfortably in an approved carrier that goes under the seat in front of you.
Can I check my dog as baggage on United?
No. United no longer takes pets through its PetSafe program. Pets only fly in cargo for some military and State Department moves, and that program now covers flights between Guam and Honolulu.
Want to read it yourself? Here is United’s own pet travel page.
The Nomad Paws is in memory of Woody, a great traveler and, most of all, the best, kindest and wisest friend I have ever had.
This is a research comparison, not a hands-on test. Every size, weight limit and price here comes from United’s own pages, the brands’ pages and the Amazon listings, read on 21 October 2026. Listings and prices change, so measure the carrier you buy and check the listing before you order.
As an Amazon Associate I earn from qualifying purchases, which costs you nothing extra and keeps these guides free to read. United makes the final call at the gate, so confirm the rules for your aircraft before you fly. This is a guide to gear and airline rules, not veterinary advice.
