The standard maximum dimension of a carry-on bag is 45 linear inches, in the form of a 22 inches by 14 inches by 9 inches. Some airlines may allow up to 55 linear inches, but this is uncommon.
Carry-on bags may not exceed 45 linear inches for most airlines, meaning that the total of the bag's height, width and depth must be equal to or less than 45 inches. Customers with large luggage or packages should check their bags, as they cannot be stored in the main cabin. Occasionally, passengers may be required to check bags even if their carry-on bags meet size and weight criteria. This happens most frequently on small aircraft in which overhead storage is limited.