Airport Carry-on Bag Size Rules: What Size Bag Is Allowed for Air Travel?

Most major U.S. airlines cap carry-on bags at 22 x 14 x 9 inches including wheels and handles, but the airline sets the rule, not the TSA.

A bag that slides into the overhead bin at home can get gate-checked on the return leg, and the difference is usually an inch of wheel height. Airport carry-on bag size rules in the U.S. come from the airline, not the government, and carriers publish their own limits. Measure a bag at the fabric shell and it may pass your closet tape measure while failing the metal sizer at the gate. The fix is simple: know the number your airline publishes, measure the full bag, and expect the gate agent to enforce the airline’s number, not a federal one.

Does TSA Set a Carry-on Size Limit?

No. TSA screens what’s inside your bag and does not set size limits for carry-on luggage. TSA’s own guidance says carry-on size restrictions vary by airline and tells travelers to check with their airline before flying.

This is the single most common mix-up. TSA’s job is security screening: what you can bring through the checkpoint and how liquids are packed. Whether your bag fits the overhead bin is an airline and aircraft question, and the airline’s published dimensions control it. A bag can clear TSA screening without any issue and still get pulled at the gate for being too large.

What Size Carry-on Do Most U.S. Airlines Allow?

22 x 14 x 9 inches is the most widely cited domestic carry-on maximum, and the FAA notes that the maximum size for most airlines is 45 linear inches total (height plus width plus depth). Both are guidelines, not a universal rule.

The 45-linear-inch figure comes from FAA carry-on baggage guidance describing the general limit across most airlines. Anything larger, the FAA says, should be checked. Individual carriers publish their own numbers, and those are the ones that decide whether you board with the bag or hand it over at the jet bridge. United, for example, publishes a limit of 9 x 14 x 22 inches (23 x 35 x 56 cm) and states plainly that handles and wheels count toward that measurement.

That extra room is real, but it applies on Southwest flights, not everywhere. A bag built to Southwest’s maximum can exceed what United, American, or Delta accept, which is exactly how travelers get surprised on a connecting itinerary booked across two carriers.

Here’s the shape of the market right now:

How Should You Measure a Carry-on Bag?

Measure the entire bag at its widest points, including wheels, handles, and any external pocket that bulges past the shell. The published limits are outer dimensions, not interior capacity.

Run a tape measure from the bottom of the wheel to the top of the extended handle, then measure width across the widest point and depth front to back with the bag packed, not empty. A soft-sided bag expands when full, and an overstuffed bag gains a half inch in every direction. If you want to skip the guesswork and buy a bag that clears the common limits with room to spare, our roundup of the best carry-on travel bags tested covers sizes that actually measure what the label claims.

United’s own carry-on page spells out the measuring method directly: include handles and wheels. United’s carry-on bag policy is the clearest published example of how airlines expect you to size a bag.

Then compare your number against your specific airline’s published dimensions, not TSA’s screening guidance. If the bag exceeds the airline’s limit, plan on checking it and review that carrier’s baggage fees before you leave for the airport.

What Still Decides Whether Your Bag Boards?

Airline policy controls final acceptance, and it can tighten based on aircraft type, fare class, route, and how full the cabin is. A basic-economy ticket on a regional jet is the tightest case.

Smaller regional aircraft have smaller overhead bins, and gate agents sometimes gate-check every roller bag on those flights regardless of size. Full flights push the same button: once bins fill, the remaining bags go under the plane even when they fit the published limit. None of that is a size problem you can measure your way out of, which is why a soft-sided bag that compresses slightly beats a hard shell that’s exactly at the limit.

Last, keep the personal item separate in your head. That’s the smaller bag that slides under the seat in front of you, and its dimensions come from your airline’s policy independently of the carry-on allowance. Assuming a personal item and a carry-on share one rule is how travelers end up paying a gate-check fee on a bag they thought was covered.