The answer is - it depends. It depends on your airline, the size of your bag (length and width), whether or not you're flying with checked bags, and where you're going to be storing it/checking it when you arrive at your destination.There's a range of carry-on sizes, but these are the most common:Here are some specific guidelines for different airlines (just a few examples): Continental - dimensions of 22" x 14" x 9" and weight of 45 lbs. Southwest - dimensions of 22" x 14" x 9" and weight of 40 lbs. Delta - dimensions of 28-inches maximum length, 18-inches maximum width, 11 inches maximum depth (8 inches if the item is a personal electronic device) and weight of 50 lbs. American Airlines - dimensions of 22-inches maximum length, 14 inches maximum width, and 9 inches maximum depth (6 inches if the item is a personal electronic device) and weight of 40 lbs. United - dimensions of 20-inch standard or 22 inch economy max for domestic flights, 21 inches max for international flights, and weight of 50 pounds. Check with your airlines before you go to get bag measurements as these may change frequently!