A 20-inch suitcase is typically considered the "standard" size for carry-on luggage across most domestic and international airlines. Its physical dimensions generally measure around 50 cm x 35 cm x 23 cm (approx. 22" x 14" x 9" when including wheels and handles). This size offers a capacity of roughly 35 to 45 liters, which is ideal for a 2-to-4 day trip. In terms of visual scale, it is roughly the size of a standard microwave or a large dictionary. It is specifically designed to fit into the overhead compartments of narrow-body aircraft. While many 20-inch bags feature "expandable" zippers that add another 2 inches of depth, using this feature often makes the bag too large for "sizers" at the gate, potentially forcing a gate-check.