Different airlines have different size restrictions over carry-on baggage.
Most airlines insist that the carry-on dimensions should 22 inches x 14 inches x 8 inches including handles and wheels of the suitcase.
This is mostly the largest size of cabin suitcases that can comfortably fit into the overhead bins of the economy seats.
Larger sizes are permitted in Premier Economy, Business class and so on. Though it would be safe to ensure the suitcases we carry stay within the above dimensions.