Verify that your suitcase is a "box" with six flat surfaces that meet at right angles. When a suitcase has rounded corners, measure to where the corners would be if they were not rounded. Some suitcases will have handles that stick out even after you have pushed them in as far as they will go. With those suitcases, measure the object as if it was a box without protrusions.
Measure the length, the width and the height of the suitcase. Add these three measurements together to get the size of the object in linear inches.
Consult your airline to see if your baggage meets airline restrictions. Typically, airlines allow two checked bags and those bags cannot exceed 62 linear inches in size. Airlines usually allow one carry-on bag that does not exceed 45 linear inches.
