Pet Carrier Size Checker
Check Your Carrier Dimensions
Enter your carrier's dimensions to see if it fits in the airline cabin.
Most airlines let you bring your pet into the cabin - but only if it fits under the seat in front of you. It’s not about weight. It’s about dimensions. If your pet’s carrier doesn’t fit in that space, you’re out of luck - no exceptions, no last-minute upgrades, no pleading at the gate.
What’s the real size limit for pet carriers?
Airlines don’t all use the same numbers, but they all follow the same rule: the carrier must fit under the seat in front of you. That means the maximum size is usually around 17 x 11 x 9 inches (43 x 28 x 23 cm). Some airlines like Delta and United allow up to 18 x 11 x 11 inches, but that’s the upper limit. Anything bigger and it won’t slide under the seat, even if you push it hard.
Here’s what that looks like in real life: a small dog like a Chihuahua, Yorkie, or Pomeranian fits easily. A cat? No problem. A 12-pound Shih Tzu? Usually fine. But a 15-pound French Bulldog? That’s pushing it. Even if your dog weighs under the airline’s 20-pound limit, if the carrier is too tall or too wide, you’ll be asked to check it - and you’ll pay extra.
Pro tip: Measure your carrier before you pack. Don’t rely on the box it came in. Use a tape measure. Lay it flat on the ground and check the height, width, and depth. Then imagine it sliding under the seat. If the front edge sticks out more than an inch, it’s too big.
Weight limits matter too - but not how you think
Most airlines say pets must weigh under 20 pounds (9 kg), including the carrier. But here’s the catch: that’s not the real rule. The real rule is: if it fits under the seat, it’s fine. A 19-pound cat in a bulky carrier might not fit. A 17-pound dog in a slim, soft-sided carrier might.
Soft-sided carriers are your best friend. They’re flexible, compressible, and often have a rigid bottom to meet airline rules. Hard-sided carriers? They’re sturdy, but they’re also rigid. If the corners stick out, you’re at risk of being turned away. Airlines have strict rules because they don’t want carriers blocking foot space or getting stuck under seats during turbulence.
One traveler in Auckland brought her 16-pound rescue terrier in a soft carrier that measured 17.5 x 10.5 x 9 inches. The flight attendant checked it, nodded, and said, “Perfect fit.” Another person with a 14-pound cat in a hard carrier that was 18 x 12 x 10 inches was told to check it - even though the cat weighed less. Size, not weight, won.
Which airlines are strictest? Which are easiest?
Not all airlines treat pets the same. Here’s how the big ones stack up in 2025:
| Airline | Max Carrier Size (inches) | Max Weight (lbs/kg) | Soft-Sided Allowed? |
|---|---|---|---|
| Air New Zealand | 17 x 11 x 9 | 20 / 9 | Yes |
| Delta Air Lines | 18 x 11 x 11 | 20 / 9 | Yes |
| United Airlines | 18 x 11 x 11 | 20 / 9 | Yes |
| American Airlines | 17 x 10 x 8 | 20 / 9 | Yes |
| Alaska Airlines | 17 x 11 x 8 | 20 / 9 | Yes |
| JetBlue | 17 x 11 x 8 | 20 / 9 | Yes |
| Southwest | 18.5 x 13.5 x 8.5 | 20 / 9 | Yes |
JetBlue and American are the tightest. Southwest is the most generous - their carriers can be wider and longer, but not taller. If you’re flying internationally, check the airline’s website. Some require a health certificate, a specific carrier type, or even a reservation for your pet - and those fill up fast.
What if your pet is too big?
If your pet doesn’t fit under the seat, you have two options: check them as baggage or use a pet shipping service.
Checking your pet means they travel in a climate-controlled cargo hold. It’s safe, but stressful. Airlines like Delta and United have dedicated pet transport teams, but you still need to arrive 2-3 hours early. Fees range from $125 to $300 one-way, depending on the route. You’ll also need a hard-sided, IATA-approved carrier - and your pet will need a vet health certificate issued within 10 days of travel.
Some people choose pet shipping services like PetRelocation or PetAirways. These companies handle everything: paperwork, customs, airport drop-off, and delivery. It’s more expensive - often $500-$1,500 - but if you’re moving overseas or your pet is over 20 pounds, it’s the only way.
What about emotional support animals?
In 2025, U.S. airlines no longer recognize emotional support animals as service animals. That means ESAs are treated like regular pets. Same size rules. Same fees. Same carrier requirements. If you’re flying with an ESA, you’ll need to follow the same rules as someone bringing a cat or small dog. No special treatment. No free passes.
Some international airlines still have different rules, but if you’re flying from or into the U.S., Canada, Australia, or New Zealand, ESA rules are locked down. Don’t rely on old advice you read online. Policies changed in 2021 and haven’t loosened since.
What carriers actually work?
Not every pet carrier on Amazon is airline-approved. Look for these features:
- Soft-sided with a rigid bottom
- Water-resistant fabric
- Mesh panels on all sides for airflow
- Zippered top with a secure closure
- Handles on top and sides
- Label pockets for your pet’s ID and health papers
Popular models that consistently pass inspections: Sleepypod Air, Sherpa Original Deluxe, and Petmate Sky Kennel Soft-Sided. These are designed specifically for cabin travel. Avoid cheap, no-name carriers - they’re often too flimsy, too tall, or lack proper ventilation.
What if you’re flying with two pets?
Most airlines let you bring one pet per passenger. Some, like Alaska and Southwest, allow two if they’re small enough to fit in one carrier - but only if they’re from the same household and under 20 pounds total. You can’t bring two separate carriers unless you have two seats. And you can’t buy a second seat just for your pet. Airlines don’t allow that.
If you have two cats or two small dogs, you’ll need to check one of them. Or book two tickets. But remember: you can’t have two pets under the seat unless they’re in one carrier together. And even then, the carrier must still meet size limits.
Pro tips for smooth travel
- Book your pet’s spot early - airlines limit how many pets can fly in the cabin per flight (usually 2-4 per plane).
- Arrive at the airport 2-3 hours early. Pet check-in takes longer than regular check-in.
- Don’t feed your pet 4-6 hours before flying. Less chance of accidents.
- Bring a small towel or blanket. Some carriers don’t have absorbent bottoms.
- Label the carrier clearly: your name, phone number, destination, and “Live Animal.”
- Keep your pet’s health certificate and vaccination records in a waterproof pouch - you’ll need to show them at check-in.
One traveler in Auckland flew with her 13-pound cat to Sydney. She used a Sherpa carrier, booked her pet spot 3 weeks ahead, and arrived 2.5 hours early. She got through security without a hitch. The flight attendant even gave her a water bottle for the cat. That’s the difference between being prepared and winging it.
Final checklist before you fly
- Carrier measures under 17 x 11 x 9 inches?
- Pet and carrier combined under 20 pounds?
- Soft-sided with rigid bottom?
- Health certificate issued within 10 days?
- Pet reservation confirmed?
- Water bottle and absorbent pad inside carrier?
- Label with contact info attached?
If you checked all those boxes, you’re ready. No stress. No surprises. Just a calm flight with your pet right beside you.
Can a 20-pound dog fly in the cabin?
A 20-pound dog can fly in the cabin only if the carrier fits under the seat. Weight alone doesn’t matter - size does. A 20-pound dog in a slim, soft-sided carrier might fit. A 20-pound dog in a bulky hard carrier won’t. Always measure before you go.
Is a cat carrier the same size as a dog carrier?
Yes, the size rules are the same. Airlines don’t differentiate between cats and dogs. A carrier for a cat must still meet the same 17 x 11 x 9 inch limit as one for a dog. The only difference is that cats usually need less space - so a smaller carrier often works better.
Can I bring my pet on a international flight?
Yes, but rules vary by country. For flights into or out of New Zealand, Australia, or the U.S., your pet must be in an approved carrier, have a health certificate, and sometimes a microchip. Some countries require quarantine. Always check the destination country’s pet entry rules before booking.
Do I need to reserve a spot for my pet?
Yes. Airlines limit the number of pets in the cabin per flight - usually 2 to 4. You can’t just show up and hope for space. Book your pet’s spot when you book your ticket, or as soon as possible after. Spots sell out fast, especially on weekends and holidays.
Can I bring two pets in one carrier?
Some airlines allow two small pets in one carrier if they’re from the same household and weigh under 20 pounds total. But you still need to follow the size rules. The carrier must fit under the seat. Never put two pets in a carrier unless you’ve confirmed it’s allowed by your airline.
