Carry-On Size Rules and TSA Liquid Limits
Last reviewed
The short answer
Two separate rule sets govern your cabin bag: the airline decides how big it can be, and the TSA decides what can go inside it. The standard US carry-on is 22 x 14 x 9 inches, but Southwest allows 24 x 16 x 10 and the ultra-low-cost carriers enforce a much smaller personal item with a physical sizer at the gate.
Key Travel Facts & Insights
- Standard US carry-on is 22 x 14 x 9 inches including wheels and handles
- TSA 3-1-1: liquids in containers up to 3.4 oz, in one quart-size bag, one bag per passenger
- United Basic Economy and several ULCC base fares include no full-size carry-on at all
- Gate-checking a bag you should have paid for at booking costs several times more
Airline size limits
The de facto US standard is 22 x 14 x 9 inches including wheels and handles — the dimension almost every hardshell "carry-on" suitcase is built to. Most US carriers use it.
The exceptions matter. Southwest allows a notably larger 24 x 16 x 10. Spirit and Frontier permit a larger cabin bag but charge for it separately. European carriers frequently impose a cabin bag weight limit — typically 8–10 kg — which US carriers generally do not, and enforce it more actively.
- Personal item: must fit fully under the seat in front of you
- Carry-on: overhead bin, sized against a gate sizer if challenged
- ULCC personal items are smaller than mainline ones — Spirit is 18 x 14 x 8
- United Basic Economy includes no full-size carry-on on domestic routes
The TSA 3-1-1 rule
Liquids, gels, aerosols, creams and pastes in your carry-on must be in containers of 3.4 ounces (100 ml) or less, all of which must fit in a single quart-sized clear resealable bag, one such bag per passenger.
The container size is what counts, not how much is in it. A half-empty 8 oz bottle is not permitted; a full 3.4 oz bottle is.
- Medications, baby formula, breast milk and juice for infants are exempt and may exceed 3.4 oz — declare them at screening
- Powders over 12 oz may require additional screening on international departures
- Solid food is allowed; spreadable food such as peanut butter, hummus and yoghurt counts as a liquid
- Ice packs must be frozen solid at screening; partially melted ones are treated as liquid
Batteries and electronics
Lithium batteries and power banks must travel in the cabin, never in checked baggage, because of fire risk. This includes spare camera batteries, laptop batteries and portable chargers.
A growing number of airlines now also require power banks to remain visible and not be used or charged during flight. Keep them in the seat pocket rather than the overhead bin.
Avoiding the gate-check charge
On carriers where the base fare excludes a carry-on — United Basic Economy, Spirit Go, Frontier Basic, Volaris Zero, Avianca XS, WestJet UltraBasic — arriving at the gate with a full-size bag triggers a charge that is typically several times what the same bag would have cost at booking.
Gate agents at these carriers use a physical sizer and enforce it consistently. The cheapest moment to buy a bag is always the moment you book; the most expensive is the gate.
When your bag gets gate-checked for free
On small regional aircraft — particularly Bombardier CRJ series flown by SkyWest and others — overhead bins genuinely cannot take a full-size carry-on. Bags are gate-checked at the jet bridge free of charge and returned at the jet bridge on arrival.
This is not a fee situation, but it does mean your bag leaves your possession. Move medication, documents, laptops, chargers and anything valuable into your personal item before you board.
Common questions
What is the standard carry-on size?
22 x 14 x 9 inches including wheels and handles at most US airlines. Southwest is more generous at 24 x 16 x 10. Many European and Asian carriers add a weight limit of 8–10 kg that US carriers generally do not impose, and enforce it more actively at the gate.
What is the TSA 3-1-1 rule?
Liquids, gels and aerosols in containers of 3.4 oz (100 ml) or less, all fitting inside one quart-sized clear resealable bag, one bag per passenger. The container size is what matters, not how full it is. Medications, baby formula and breast milk are exempt but should be declared at screening.
Which airlines do not include a carry-on?
United Basic Economy on domestic routes, Spirit Go, Frontier Basic, Allegiant standard fares, Volaris Zero, Avianca XS on many routes, and WestJet UltraBasic. On all of these the carry-on is a separate purchase, and buying it at the gate costs far more than buying it at booking.
Related
More in Baggage
Need help with your own booking?
Our US travel consultants handle changes, cancellations, refunds and claims directly. No charge to ask.