TL;DR: 1) Before flying, always check your airline’s carry on luggage size and weight guidelines. A good rule of thumb is that your carry on luggage can be up to 45 linear inches (length + width + height, roughly 22 x 14 x 9 inches). The most common configuration is 22 x 14 x 9 inches. 2) Keep your luggage to under 25 pounds (10kg). 3) Your toiletries must be in 3.4 oz (100 ml) or smaller bottles. Those bottles must be in a single quart-sized, clear, plastic, zip-top bag.