This means that when measuring luggage for size, whether it's for checked or hand luggage, you always have to include wheels, ...

That's why when looking at the product descriptions, always look for the "overall size". At the check-in desks, checked ...

For example, American Airlines' carry-on luggage size is 22 x 14 x 9, while Southwest allows a slightly larger carry-on measuring 24 x 16 x 10. While carry-on luggage sizes can vary by airline ...