International carry-on size and weight limits

Most international airlines allow a cabin bag of roughly 55 x 40 x 23 cm (about 22 x 16 x 9 in) and — unlike US domestic carriers — enforce a weight limit, commonly 7 to 10 kg. The dimensions are close enough to the US standard that a well-chosen carry-on usually fits. The weight limit is what actually catches travelers out, because it includes the empty bag.

That single fact should change what you buy. If a carrier caps you at 7 kg (15.4 lb) and your hardside spinner weighs 3.5 kg (7.7 lb) empty, half your allowance is gone before you pack a shirt. On a 10 kg allowance a sub-6 lb bag hands you back three or four kilos of actual clothing. This is the single strongest argument for a lightweight carry-on if you fly internationally with any regularity.

The regional pattern

Rather than memorize 100 carriers, learn the three patterns. They cover almost every airline you will fly.

*US carriers publish no cabin-bag weight limit for most fares. Figures are the carriers' own published limits and change without notice — always confirm on the airline's baggage page before you fly. Our carry-on size by airline table lists the exact published figures carrier by carrier.

The 7 kg problem

A 7 kg cabin allowance is the strictest common international rule, and it is normal across much of Asia-Pacific and the Middle East. Seven kilograms is 15.4 pounds including the suitcase. Run the arithmetic before you buy:

• A 3.5 kg (7.7 lb) hardside spinner leaves you 3.5 kg of packing.
• A 2.5 kg (5.5 lb) lightweight softside leaves you 4.5 kg — nearly 30% more.
• A 2.0 kg (4.4 lb) cabin backpack leaves you 5 kg.

That is the whole game on weight-capped routes, and it is why empty weight leads every spec chip in our roundups. If you fly these carriers often, a soft bag or a carry-on backpack is usually the smarter buy than a heavy molded shell.

Why the depth number is the one that fails

European low-cost carriers converge on a 20 cm depth, against the US standard's 23 cm. Three centimeters sounds trivial, but depth is exactly where an expanded or overstuffed softside bag grows, and it is the dimension the drop-in gate sizer measures most unforgivingly. A bag that slides into a US sizer can jam in a Ryanair one purely on depth.

Two practical consequences. First, never fly a budget European carrier with the expansion zipper open. Second, if you buy specifically for these routes, look for a case whose stated depth is 20 cm or less including wheels — not a 23 cm bag you intend to under-pack.

Personal items and the second bag

Most international carriers also allow a personal item that must fit under the seat, and the low-cost carriers have made that the onlyfree bag on basic fares. Ryanair's free allowance, for instance, is a small under-seat bag; the 55 x 40 x 20 cm cabin bag requires paid priority. Sizes vary more than carry-on limits do, so check our personal item size by airline table and consider an underseat bag sized to the strictest carrier you fly.

How to make an international carry-on work

1. Buy for the strictest airline you actually fly, not the average one. A 55 x 40 x 20 cm bag is legal nearly everywhere; a 24-inch US bag is not.
2. Weigh the empty bag yourself on a bathroom scale before the trip. Published weights are sometimes for a different size in the range.
3. Wear the heavy items — boots and a coat on your body do not count toward a cabin weight limit.
4. Keep the expansion zipper closed on European budget routes.
5. Check the carrier's own page within a week of flying. These limits change, and the gate agent uses today's rule, not the one you read last year.

For the packing side of this — how to get a week into a bag that small — see how to pack a carry-on.