In 2026, most major airlines have standardized their carry-on wheel height to be approximately 2 inches (5 cm), which must be included in the bag's total height measurement. Most domestic and international carriers enforce a limit of 22 x 14 x 9 inches (56 x 36 x 23 cm). Because these dimensions include everything from the handle to the wheels, luggage manufacturers typically design the "box" of the suitcase to be about 20 inches tall so that the 2-inch wheels don't push the bag over the limit. For 2026 travelers, "spinner" wheels (four wheels) are the most popular, but they often take up more of your precious vertical allowance than "inline" wheels (two wheels). Always double-check your specific airline's "sizer" rules, as a wheel that protrudes even half an inch too far can result in a forced gate-check and a surprise fee, especially on budget carriers like Ryanair or Spirit.