The flights of which airlines you will take? And usually the size of each carry-on luggage should be smaller than 20 X 40 X 55 centimeter (7.8 X 15.7 X 21.6 inches) and total weight should be less than 5 kg (11 pounds). But sometimes it varies from different airlines. Thus, it is better for you to refer to the carry-on luggage regulations of the exact airlines.