Though you might find an inch or two of a difference with various airlines, the standard domestic carry-on luggage size is 22" x 14" x 9", which includes the handle and the wheels. This size limit ensures your bag — and ideally everyone else's — will be able to be stored safely in the overhead bin for your flight.
What size is a carry-on suitcase for American Airlines?
22 x 14 x 9 inCarry-on should not exceed the following size and weight restrictions: 45 linear inches (22 x 14 x 9 in) or 115 centimeters (56 x 36 x 23 cm) including handles and wheels. Fit in the overhead bin or under the seat in front of you. Personal item should be of proper size to fit under the seat in front of you.