Airline Carry-On Size Chart
Most major US airlines allow the same 22 x 14 x 9 inch carry-on, but Southwest allows a larger bag, and the real change in the last couple of years is not the size limit itself but how strictly gate agents now measure it. This chart lists the standard limits and what has changed about enforcement, since a bag that fit fine a few years ago at the gate may not pass a sizer today.
Standard carry-on limits by airline
American, Delta, and United: 22 x 14 x 9 inches (56 x 35 x 23cm), including wheels and handles. This is the de facto US industry standard that most hard-shell and soft-shell carry-on luggage is designed around.
Southwest: 24 x 16 x 10 inches (61 x 41 x 25cm), noticeably larger than the standard three-airline limit, giving Southwest flyers real extra packing room for the same 'carry-on' category.
Personal item (all airlines): roughly 17 x 10 x 9 inches (43 x 25 x 23cm) for most carriers, meant to fit under the seat in front of you rather than in the overhead bin, though exact personal item limits vary more between airlines than carry-on limits do.
Basic economy fare restrictions: some airlines' cheapest fare tiers only include a personal item, with a full carry-on requiring an upgrade or an add-on fee, so check your specific fare class rules, not just the airline's general carry-on policy.
Why enforcement has tightened, not the limits
The size limits themselves have not changed meaningfully in years, but airlines have shifted from an honor-system approach to measuring bags at the gate with dedicated sizer frames and, increasingly, automated scanners that check dimensions without a gate agent's judgment call involved. A bag that used to squeeze past a quick visual check is far more likely to get caught now.
This shift matters most for soft-shell and slightly overstuffed bags, since a bag that flexes or bulges past its stated dimensions when packed full is exactly the kind of near-miss that stricter measurement catches, while it might have passed an eyeball check in the past.
Always verify before a specific trip
Airline size policies are not standardized by any single regulatory body and each airline sets and can change its own limits, so treat any chart, including this one, as a starting reference and check your specific airline's current published policy before a trip, especially on international carriers or budget airlines that often run smaller limits than the major US carriers.
If you fly multiple airlines regularly, sizing your everyday carry-on to the smallest limit you commonly encounter, rather than the most generous one, means you never have to think about which airline you are flying before packing.