Know it fits before you get to the gate
Under-seat carriers listed with all three measurements — length, width and height — checked against what nine U.S. airlines publish themselves.
The numbers, up front
Every carrier lists its length, width and height. Every backpack lists the size of dog it is built for.
Ships from the U.S.
California and Nevada warehouses, 1–5 business days. Alaska, Hawaii and Puerto Rico included.
The fit guarantee
If a carrier does not clear the limit we published for your airline, we refund it and pay the return.
Ask before you buy
Send your pet's measurements. We answer with a size, not a sales pitch.
Pick your airline. See what actually fits.
Nine U.S. airlines, nine different under-seat limits. Length and width are fixed by the space itself, so a carrier has to clear those as it is. Height is the one figure with any give, and we allow one inch of it — no more.
- Soft-sided max
- —
- Hard-sided max
- —
- Weight limit
- —
Read on the airline’s own policy page, 26 August 2026. Open the official page
Mr. Peanut's Gold Series Low-Profile
16 × 10 in footprint · 10 in tall · up to 12 lb
Checking against the published figures
$119.99
Under-Seat Carrier
17 × 9 in footprint · 11.5 in tall · up to 15 lb
Checking against the published figures
$36.99
Travel Carrier — 17 in
17 × 10 in footprint · 11.5 in tall · up to 15 lb
Checking against the published figures
$35.99
Soft Carrier Bag — 17 in
17 × 9 in footprint · 11.5 in tall · up to 15 lb
Checking against the published figures
$39.99
Cabin Carrier — 17 in
17 × 11 in footprint · 11 in tall · up to 11 lb
Checking against the published figures
$34.99
Mr. Peanut's Gold Series Carrier
18 × 10.5 in footprint · 11 in tall · up to 15 lb
Checking against the published figures
$109.99
Mr. Peanut's Gold Series Expandable
18 × 10.5 in footprint · 11 in tall · up to 15 lb
Checking against the published figures
$119.99
Mr. Peanut's Diamond Series
18 × 11 in footprint · 11 in tall · up to 15 lb
Checking against the published figures
$79.99
Mr. Peanut's Platinum Series
18 × 10.5 in footprint · 11 in tall · up to 15 lb
Checking against the published figures
$84.99
Backpack Carrier Backpack
16.5 × 12.5 in footprint · 10.5 in tall, lying on its back · up to 25 lb
Checking against the published figures
$49.99
Pet Backpack Backpack
17 × 13 in footprint · 12 in tall, lying on its back · up to 16 lb
Checking against the published figures
$59.99
How we count. The footprint has to clear as it is — a bag does not get narrower. On the height we allow one inch of squash, because a soft top gives a little under a seat. One inch, not four: a bag three inches over the published height is not going under anything, and we are not going to pretend otherwise. Confirm the policy with your airline before you book, and remember the rule a gate agent actually applies — your pet must be able to stand up and turn around inside.
The two backpacks are in this list on purpose. They are measured lying on their back, because that is the only way a backpack goes under a seat, and on those figures each one clears exactly one of the nine: Frontier. Everywhere else they do not fit under a seat, so they are not a way to fly with your pet, and the tool will tell you which airline is refusing them and by how much.
Every cabin carrier we sell, in one table
“Clears” counts how many of those nine airlines this bag gets under: the footprint as published, and the height with at most one inch of squash. Nobody clears Breeze — its published width is 8 inches, narrower than anything we sell. Two of the rows are backpacks, marked as such: they are measured lying on their back, which is the only way a backpack goes under a seat, and on those figures each of them clears exactly one airline. That one airline is Frontier, and the row says so rather than hiding it.
| Carrier | Footprint (L × W) | Height | Pet up to | Clears | Price |
|---|---|---|---|---|---|
| Mr. Peanut's Gold Series Low-Profile The lowest of our zip-top cabin bags | 16 × 10 in | 10 in | 12 lb | 6 of 9 | $119.99 |
| Under-Seat Carrier The long, narrow one · side entry | 17 × 9 in | 11.5 in | 15 lb | 5 of 9 | $36.99 |
| Travel Carrier — 17 in Mesh on the top and both sides | 17 × 10 in | 11.5 in | 15 lb | 5 of 9 | $35.99 |
| Soft Carrier Bag — 17 in Opens from the top mid-flight | 17 × 9 in | 11.5 in | 15 lb | 5 of 9 | $39.99 |
| Cabin Carrier — 17 in Waterproof wipe-clean nylon · side entry | 17 × 11 in | 11 in | 11 lb | 5 of 9 | $34.99 |
| Mr. Peanut's Gold Series Carrier Self-locking zippers · plywood base · 2.9 lb empty | 18 × 10.5 in | 11 in | 15 lb | 5 of 9 | $109.99 |
| Mr. Peanut's Gold Series Expandable Same bag to fly, opens out after you land · 3.2 lb empty | 18 × 10.5 in | 11 in | 15 lb | 5 of 9 | $119.99 |
| Mr. Peanut's Diamond Series Two expansion bays for after you land | 18 × 11 in | 11 in | 15 lb | 5 of 9 | $79.99 |
| Mr. Peanut's Platinum Series Two expansion bays · 300D nylon · 2 lb empty | 18 × 10.5 in | 11 in | 15 lb | 5 of 9 | $84.99 |
| Backpack Carrier Backpack Backpack · measured lying on its back, which is the only way it goes under a seat | 16.5 × 12.5 in | 10.5 in | 25 lb | 1 of 9 | $49.99 |
| Pet Backpack Backpack Backpack · measured lying on its back, which is the only way it goes under a seat | 17 × 13 in | 12 in | 16 lb | 1 of 9 | $59.99 |
Under-seat carriers
Every one lists its exact footprint. Compare it against your airline before you buy.
Mr. Peanut's Gold Series Expandable — 18 × 10.5 × 11 in, Deja Blue
$119.99
Mr. Peanut's Gold Series Low-Profile — 16 × 10 × 10 in, Up to 12 lb
$119.99
Soft Carrier Bag — 17" or 19", Top Access, Up to 15 lb
$39.99
Cabin Carrier — 17 × 11 × 11 in, Wipe-Clean Nylon
$34.99
Mr. Peanut's Diamond Series — 18 × 11 × 11 in, Double Expandable
$79.99
Under-Seat Pet Carrier — 17 × 9 × 11.5 in, Up to 15 lb
$36.99
Travel Carrier — 17", Side Entry & Seat-Belt Loop
$35.99
Mr. Peanut's Gold Series Carrier — 18 × 10.5 × 11 in, Charcoal Ash
$109.99
Every figure on this page was read on the airline’s own policy page, and the guide shows the source for each one.
Read the airline guide
The thirty seconds nobody warns you about
At security your carrier goes through the X-ray machine and your pet does not. For half a minute you are holding a frightened animal in the loudest room in the airport, in socks, with a queue behind you. That is when pets are lost in terminals — and it is the reason this kit exists. The harness is not an accessory to the carrier. It is the backup for the one moment the carrier cannot do its job.
- The carrier — soft-sided, side entry, washable pad, seat-belt loop. Choose your size and color.
- The harness — padded and reflective, adjustable at neck and chest, with a control handle on the back.
- The hands-free lead — 48 in stretching to 60 in, with a bungee section and an adjustable waist belt.
- One box, one warehouse, one tracking number.
The backpack kit
Hands-Free Kit — backpack, harness and waist lead
For the trips where the carrier goes on your back: trails, transit, the walk between terminals. Same harness and same lead as the Cabin-Ready Kit, with the backpack in place of the under-seat bag.
$89.99$99.93
Save $9.94
The car kit
Road-Trip Kit — booster seat, harness and waist lead
For the car. A booster seat that lifts a small dog to window height, the same harness for the tether to clip to — never the collar — and the same lead for every stop along the way.
$79.99$89.93
Save $9.94
Where are you taking them?
The gear splits cleanly. What fits under an airline seat is not what works in a car, and neither is what you wear on your back up a trail. Pretending otherwise is how people end up posting things back.
Flying with your pet
Under-seat carriers, the harness for the security line, and the pads you will be glad you packed.
Shop cabin gear
Road trips
Booster seats, tethers and covers. A loose dog in a moving car is the risk nobody plans for.
Shop car gear
Hiking and trails
Backpacks you wear. Your dog rides on your back, both hands stay free, and the size is set by their back length.
Shop backpacks
Kits and bundles
The pieces that belong together, in one box and at one price.
Shop kits
Small things that make the trip easier
The pieces people email us about after the first flight.
The six questions we get every week
If yours is not here, write to us. We answer with numbers.
No carrier is, anywhere. Airlines do not approve or certify pet carriers — they publish a maximum size for the space under the seat and leave it to you to buy something that fits. That is why you will not see the phrase on this site, and why every listing gives you exact measurements instead.
Use the finder above: pick your airline and it will tell you which of our carriers fits, and by how much the others miss.
It matters, and we count it. The space under an airline seat is a fixed rectangle, so length and width have to clear as published — a bag 19 inches long does not become 18. Height is the only measurement with any give: a soft top compresses a little, which is why airlines recommend soft-sided bags in the first place.
We allow one inch of that compression and no more. So JetBlue, which publishes 8.5 in, rules out most soft carriers on the market, and we say so instead of showing you a green tick that falls apart at the gate.
Measure your pet lying down, from the nose to the base of the tail, and add 2 inches. Then measure standing, floor to the top of the head. Your pet has to be able to stand up and turn around inside — that is the rule a gate agent actually applies.
Between two sizes, take the bigger interior — but only if its exterior still clears your airline. If you would rather someone checked: email us the measurements and the airline, and we will tell you which one to buy.
Everything ships from warehouses in California and Nevada, typically 1–5 business days depending on where you are. Free on every order, no minimum. Alaska, Hawaii and Puerto Rico are included at the same price — allow a few extra days for those three. We ship within the United States only.
The Mr. Peanut's Gold Series. It uses self-locking zippers that cannot be pushed open from the inside, which is the one thing cats defeat on cheaper bags — not the door, the zip they nose open while you are looking at the departures board.
Yes — 30 days from delivery, unused and in the original packaging. Email us before you post anything so we can send you a return authorisation and the correct warehouse address.
The pre-flight checklist
Everything to do in the four weeks before you fly with a pet, in the order you have to do it. We wrote it because we could not find a good one. Leave your email and we will also send you 10% off your first order.
- When to call the airline, and what to say when you do
- The paperwork each airline asks for, and how far in advance
- How to get a cat used to a carrier in the two weeks before a flight
- What happens at security, step by step, so nobody improvises