Pet Carrier Size Calculator

Updated November 2026 · free, works in your browser

To choose the right pet carrier size, measure your pet's length, height and shoulder width, then add room to stand, turn and lie down. This calculator turns those measurements into minimum carrier dimensions and a size class for car or airline travel.

How to use the pet carrier size calculator

1. Pick metric (cm, kg) or imperial (in, lb).
2. Measure your pet's length from the tip of the nose to the base of the tail while it stands naturally.
3. Measure height from the floor to the top of the head or the tips of the ears, whichever is higher.
4. Measure shoulder width across the widest part of the shoulders and enter the current weight.
5. Read the minimum carrier length, width and height and the suggested size class. The results update as you type.

How it is calculated

The method follows widely used airline guidance for pet containers: the animal should be able to stand up, turn around naturally and lie down comfortably.

• Minimum length = pet length + ½ × elbow height. Elbow height is estimated here as half of the pet's standing height, so length = pet length + 0.25 × height.
• Minimum width = 2 × shoulder width.
• Minimum height = standing height of the pet, measured to the top of the head or ears.

Results are rounded up to the next whole centimetre, or the next half inch in imperial mode. The size class is a rule of thumb: the tool checks the minimum length and the weight separately and shows the larger of the two classes.

These classes are a general guide only. Manufacturers and airlines use their own size labels and limits.

Frequently asked questions

What size carrier should I get for my dog?

Choose a carrier whose inside dimensions are at least the minimums shown by the calculator. Check the inside measurements, not the outside ones, because padding and walls take up space.

Should I size up for a kitten or puppy?

A young animal will grow, so measure again before each trip. A carrier that is only slightly too big is usually better than one that is too small, but a very large carrier can let the pet slide around during travel.

Do airlines use the same carrier size rules?

No. Each airline sets its own maximum carrier size and combined weight for in-cabin travel, and hold travel has separate container requirements. Check the airline's current rules before you book and again before you fly.

Does the carrier height matter for cats?

Yes. A cat should be able to sit upright without its ears or head touching the roof. If the cat is in a soft carrier, measure the height with the carrier fully open.

Is a bigger carrier always more comfortable?

Not necessarily. Many pets feel safer in a snug space where they can stand, turn and lie down but are not thrown around by movement. Under-seat carriers also have strict size limits.

Planning a trip with your pet

Once you know the carrier size, you can plan the rest of the journey around it: how the carrier fits in the car or under a seat, how long the pet will be inside it, and where you will stay. Accommodation that welcomes animals often lists its pet rules by destination, so compare those details early, before you commit to dates.