The size of a carry-on bag can vary slightly depending on the airline, but the standard size for most domestic airlines is around 22 x 14 x 9 inches. This means that the length, width, and height of the carry-on bag should not exceed these dimensions, including handles and wheels. Additionally, the combined length, width, and height of the baggage must not exceed 45 linear inches. Its important to note that some international carriers may have slightly different size restrictions, such as 21.5 x 15.5 x 9 inches. Its always best to check with the specific airline you are traveling with to ensure that your carry-on bag meets their size requirements.