Sizing

How to measure your pet

Four minutes with a tape measure now beats a return label later. Here is exactly what to measure and what to compare it against.

Find a carrier that fits

You need two numbers, and a third if your airline weighs

1. Length

Get your pet to lie down. Measure from the tip of the nose to the base of the tail — where the tail meets the body, not the end of it. Add 2 inches. That is the interior length the carrier needs so your pet can lie flat without curling into a shape they cannot hold for four hours.

2. Height

Now with your pet standing, measure from the floor to the top of the head — ears up if they hold them up. This is the number that decides whether they can stand inside the bag, which is the test a gate agent applies.

3. Weight

Stand on your bathroom scale. Note the figure. Pick up your pet and stand on it again. The difference is their weight. Some airlines count the carrier in the limit, so add another 2 to 4 pounds for the bag before you compare.

Then compare, in this order

  • Your airline's published length, width and height against the carrier's exterior footprint. This decides whether the bag goes under the seat.
  • Your pet's length against the carrier's interior length. This decides whether they are comfortable.
  • Your pet's standing height against the carrier's interior height. This decides whether the gate agent is satisfied.

Three things worth knowing

Interior is always smaller than exterior. Fabric, padding and a base insert eat between half an inch and an inch on every side. Most listings do not say this. Ours do.

Cats measure shorter than they look. A cat that seems enormous asleep is usually 15 to 17 inches nose to tail base. Measure before you assume you need the biggest bag.

Between two sizes, take the bigger interior — then check that bag’s exterior against your airline. A bigger bag is only better if it still clears the published limit. It is the exterior that the space under the seat cares about, and the footprint does not compress at all.

Buying here

Measurements first, adjectives second

Sized before it is listed

Every carrier lists a length, width and height. Every backpack lists the back length and the weight limit it is built for.

Ships from inside the U.S.

California and Nevada. Free on every order, no minimum — Alaska, Hawaii and Puerto Rico included.

Ask before you buy

Email your pet's measurements and the airline you are flying. We answer with a size.

Free, one page

The pre-flight checklist is free, and it is already online

Everything to do in the four weeks before you fly with a pet, in the order you have to do it. Read it now — no email needed. Leave your address and we will send you a 10% code for your first order — plus a warning if your airline moves its published limit before you fly.

  • 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 two weeks
  • What happens at security, step by step