How big should a cat carrier be?

A typical adult cat of 4 to 5 kg needs a carrier of at least 40 × 30 × 30 cm. But that figure is only a starting point: two cats of the same weight can differ by ten centimetres in length. The only reliable way to know how big your cat carrier should be is to measure your own cat — three measurements, five minutes, and you've ruled out half the catalogue.

The three-step test

Whatever its stated size, a carrier is the right size if your cat can do these three things in it:

1. Stand up without lowering their head or brushing the roof.
2. Turn round on the spot, without contorting.
3. Lie down on their side without touching both sides at once.

These are in fact the same criteria airlines use to approve a carrier for the cabin. If any one of the three fails, the carrier is too small — even if the cat “fits inside”.

How to measure your cat

Use a soft tape measure, with your cat relaxed. Three measurements are enough:

• Length — from the tip of the nose to the base of the tail (not to the tip of the tail). This is the measurement that matters most.
• Height — from the floor to the top of the head, with your cat sitting. This is what decides whether they'll be able to stand up.
• Width — from one shoulder to the other, with your cat standing and facing you.

Then add the margins: +10 cm on length, +5 to 10 cm on height, a few centimetres on width. These margins give you the minimum internal dimensions of the carrier. Watch out here: many product pages give the external measurements, and the difference can reach 3 to 4 cm on a padded model.

For reference, our city backpack measures 33 × 25 × 39 cm: an upright format, which compares differently from a long carrier with similar dimensions.

An upright format for the average cat
33 × 25 × 39 cm and 1.34 kg empty: it suits cats of an average build, up to about 6 kg. Measure yours rather than going by their weight alone. Discover the city backpack →

Guideline sizes by build

Large breeds — Maine Coon, Norwegian Forest Cat, Siberian, Ragdoll — outgrow standard sizes, and that's where most carriers on the market fall short. We cover this case separately in choosing a large cat carrier.

The too-big carrier trap

Nobody ever mentions it, yet it spoils a lot of journeys. In an oversized space, a cat has nothing to brace against: they slide at every bend, catch themselves, then slide again. That constant jostling is a source of stress in its own right, and it makes motion sickness worse.

A cat wants to wedge themselves in. The right carrier is one where they touch two sides when curled up — not one where they could take three steps. If you've bought too big, a firm cushion along one side puts things right.

Kittens: don't buy twice

A kitten adopted at three months will reach adult size in eight to ten months. Buying a carrier for their current size means buying another one the following year.

Another useful reference: our clear bubble backpack measures 32 × 29 × 42 cm for a cat up to 6 kg — an upright format, which can't be compared directly with a long carrier of similar dimensions.

The right approach: go for the size of their estimated adult build — the breed and the size of the parents are a good clue — and reduce the space for now with a rolled-up blanket along one side. Take it out bit by bit as they grow.

Cabin dimensions, a special case

If you're planning to fly, the constraint no longer comes from your cat but from the seat in front, which the carrier has to slide under. Many airlines hover around 46 × 28 × 24 cm, but the figures vary from one airline to another and change regularly.

Two practical consequences: a soft carrier, which squashes slightly, fits where a rigid one won't; and a big cat is sometimes simply incompatible with cabin size. Check the exact dimensions with your airline before booking, and read flying with your cat in the cabin for the rest of the rules.

What size doesn't solve

A perfectly sized carrier that your cat has never been inside before the big day is still a hostile object. Size determines their comfort during the journey; getting them used to it determines whether they'll agree to go in at all. The two are worked on separately — see getting your cat used to their carrier.

Sizes at Pelux

Two models cover the two ends of the range:

• The top-opening carrier is aimed at cabin size, around 46 × 28 × 28 cm — check it against your airline's limits. Its rigid base keeps the bag's shape even when loaded, which avoids exactly that “cat squashed at the bottom” effect.
• The wide-opening backpack measures 36.5 × 28 × 43 cm and takes cats up to 8 kg: it's the model designed for the builds that standard sizes leave out.

All our carriers are together in the Outdoors & adventure collection. To weigh them up on every criterion — opening, ventilation, safety, format — our guide to choosing a cat carrier goes through them in order of importance.