In 2026, the global standard for a cabin (carry-on) bag is 55 x 40 x 20 cm (including wheels and handles), which totals 115 linear centimeters. This is the official limit for major international carriers like Lufthansa, Air India, and Emirates, as well as many U.S. carriers (translated from 22 x 14 x 9 inches). However, budget airlines like Ryanair and EasyJet have introduced a "dual-tier" system where a standard free "personal item" must fit within 40 x 25 x 20 cm to go under the seat, while any bag larger than that—even a standard 55cm bag—requires a paid "Priority" upgrade. A high-value peer tip for 2026: many airports now use automated 3D scanners at the gate that measure bags instantly; if your bag is even 1 cm over the limit, the system will flag you for a mandatory gate-check fee (often $60–$100). Always check the specific dimensions for your carrier on their mobile app before heading to the airport to avoid the "sticker shock" of last-minute baggage charges for an oversized carry-on.