The dimensions of a carry-on bag vary by airline, however in the United States, the generally recognized measurements are 22′′ x 14′′ x 9′′ (55cm x 35.5cm x 23cm), including the handles and wheels. Choose a cabin bag that is 21′′ (53cm) or less in height if you want to be sure it makes it on board foreign flights. In any case, it’s usually a good idea to double-check with your airline beforehand.