Knowing that the Frontier Airlines size of carry on will assist you organize for your trip and keep needless stress and costs. The size requirements that Frontier requires for carry-on baggage are 24 inches in height, 16 inches in width, and 10 inches in depth. You may be required to check your bag in and pay an extra cost if it is larger than these limits. It is an excellent option to measure your baggage ahead of time in order to be consistent with the airline's guidelines.