A carry-on bag is one you can take aboard the airplane and stow in the overhead bin. To avoid being forced to check your suitcase for later retrieval on the conveyor belt, buy a bag that conforms to the strictest rules in the industry.
Any suitcase larger than carry-on size must be checked. The most common size options are 24 to 30 inches in height. You can find suitcases as large as 36 inches, but check with your carrier for size limits.
If your kit and caboodle has seen some mileage, buying new gear can be a money-saver in the long run. And toting the right type of luggage to fit current-day airline luggage rules will help you avoid extra fees and enable you to comply with carry-on restrictions and check-in weight limits.