Why there is no universal carry-on size
Cabin baggage limits are set by each airline for its own aircraft, not by any regulator: a small regional jet's overhead bins are physically smaller than a wide-body's, and low-cost carriers use tight limits partly to keep boarding fast and partly to sell checked baggage. The closest thing to a standard is the IATA guideline of 56 × 45 × 25 cm, which many full-service airlines have adopted — but it is a guideline, not a rule, and plenty of carriers depart from it. Budget airlines in particular tend to be smaller in one dimension (often depth, at 20 cm rather than 25 cm), which is exactly the dimension travellers forget to check. Treat every figure below as commonly published and typical, and always verify against your airline's own baggage page before you travel, because limits change.
Common carry-on limits by airline (typical, check before flying)
Dimensions include wheels, handles and pockets, as airlines measure them. Weight limits and whether a second small personal item is included vary by fare type — a basic fare and a priority fare on the same airline can have different allowances.
| Airline / guideline | Typical cabin bag (cm) | Typical weight |
|---|---|---|
| IATA guideline | 56 × 45 × 25 | — |
| British Airways | 56 × 45 × 25 | 23 kg |
| easyJet | 56 × 45 × 25 | No set limit (must be liftable) |
| Jet2 | 56 × 45 × 25 | 10 kg |
| Ryanair (priority cabin bag) | 55 × 40 × 20 | 10 kg |
| Wizz Air | 55 × 40 × 23 | 10 kg |
| Emirates | 55 × 38 × 20 | 7 kg |
| US domestic typical (e.g. major US carriers) | 56 × 36 × 23 | Varies |
How airlines actually measure
Airlines measure the bag as it travels: wheels, extended handles, side pockets and any bulging count, and sizers at the gate are rigid boxes, not tape measures — a soft bag that squashes to fit the sizer passes, a hard bag 1 cm over does not. Measure your packed bag, not the empty one on the manufacturer's page: packing adds centimetres, especially in the depth dimension. If your bag is borderline, pack it, stand it upright, and measure all three sides at their widest points, including the wheels at the bottom.
Cabin bag versus personal item
Most airlines allow a second, smaller personal item — a handbag, laptop bag or small backpack — but its allowed size is smaller still, typically around 40 × 30 × 20 cm on budget carriers and 40 × 30 × 15 cm on some full-service ones, and on the cheapest fares it may be the only bag included at all. On Ryanair's basic fare, for example, the included bag is the small personal item, and the larger 55 × 40 × 20 cm cabin bag requires priority boarding. Read the fare, not just the airline: the same carrier's allowance changes with the ticket you bought.
Packing to stay inside the limit
Choose the bag for your strictest airline, not your favourite one, if you fly more than one carrier on a trip — a bag sized for a 56 × 45 × 25 cm airline will be caught out by a 55 × 40 × 20 cm one. Soft-sided bags forgive a centimetre; hard shells do not. Weigh the packed bag at home: gate fees for an overweight or oversized bag are routinely several times the price of checking it in advance, and they are charged at the gate, where you have no good options left.
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