How Many Ounces Can You Carry On a Plane?

Baggage is one of the most common places travelers get an unpleasant surprise at the airport — not because the rules are secret, but because they vary by airline, fare class, and route more than people assume. The liquid limit is set by security, the bag dimensions by the airline, and the fees by your fare class.

The short answer

You can carry 3.4 ounces (100 ml) per container. In the US, the TSA limits liquids, aerosols, gels, creams, and pastes in carry-on bags to containers of 3.4 oz (100 ml) or less, and all of them must fit inside a single clear 1-quart bag — one bag per passenger. The limit applies to the container's size, not how full it is, so a half-empty 6 oz bottle still gets discarded.

How many ounces can you carry on a plane?

This is the question that catches the most people, and the answer is set by security, not by the airline.

The 3-1-1 rule

In the US, the TSA limits carry-on liquids, aerosols, gels, creams, and pastes to containers of 3.4 ounces (100 ml) or less. Those containers must fit inside a single 1-quart clear plastic bag, one bag per passenger, and the bag goes in the security bin separately from your luggage.

The limit is on the container size, not the amount of liquid left in it. A half-empty 6 oz bottle still counts as 6 oz and will be discarded at security. If it does not fit in the quart bag, it cannot go in your carry-on.

What is exempt from the limit

• Medically necessary liquids — prescription and over-the-counter medications, insulin, and similar items are allowed in larger quantities, but must be declared to the officer at the checkpoint.
• Baby formula, breast milk, and juice — permitted in quantities larger than 3.4 oz and do not need to fit in the quart bag.
• Duty-free liquids purchased after security, in a sealed tamper-evident bag with the receipt.

International differences

The 100 ml limit is an international standard, but enforcement details vary by country and airport. Some airports require the liquids bag to be removed from your bag; others use scanners that allow it to stay packed. If you are connecting through a non-US airport, expect the local rule to apply at that checkpoint.

Typical carry-on size limits

Most major US airlines allow a carry-on bag around 22 x 14 x 9 inches (roughly 56 x 36 x 23 cm), plus one personal item — a purse, backpack, or laptop bag — that fits under the seat.

This is not universal. Some airlines, particularly budget carriers, use smaller dimensions or charge separately for a full-size carry-on, treating only the personal item as free. Always check your specific airline's published dimensions rather than assuming the "standard" size applies.

Check in luggage size: what checked bags are allowed

Checked bags are measured by linear dimensions — length plus width plus height added together.

• Standard checked bag: typically up to 62 linear inches (158 cm), which corresponds to a common size like 27 x 21 x 14 inches.
• Oversize bags: anything above that threshold usually triggers an oversize fee, and very large items may need to be shipped as cargo instead.
• Weight: commonly 50 lbs (23 kg) per bag on domestic flights, with many international routes allowing 50 lbs in economy and 70 lbs (32 kg) in premium cabins. Budget carriers often set lower limits and charge steeply for going over.

Weigh your bag at home if you are anywhere near the limit. Overweight fees are among the highest per-pound charges in travel, and a scale is cheap.

Why Basic Economy changes things

On several major US airlines, Basic Economy fares restrict you to a personal item only, with no full-size carry-on included. Bringing a standard roller bag to the gate on one of these fares can mean an unexpected gate-check fee — usually more than you would have paid to check it online. Confirm your specific fare's carry-on allowance before you pack, not after you reach the gate.

What checked bags actually cost

• Domestic US: most major carriers charge for the first checked bag on standard economy fares. International flights sometimes include one free checked bag depending on the airline, route, and fare class.
• Pay online, not at the airport: almost every airline charges less when you add a bag during check-in online rather than at the counter. The difference is often substantial.
• Elite status and co-branded credit cards frequently waive the first checked bag fee — worth checking if you fly one airline regularly.
• Compare fees as part of the fare. A cheaper ticket on an airline that charges more for bags can cost more overall. Add the bag fee (and the carry-on fee, on budget carriers) before deciding which fare is actually cheaper.

How to avoid baggage surprises

1. Check your specific airline's current carry-on and checked-bag policy before packing, especially on a fare you have not flown before.
2. Confirm whether your fare class allows a full-size carry-on — Basic Economy and budget-carrier fares are the most likely to restrict it.
3. Pack liquids in containers of 3.4 oz or less, in one quart bag, and put that bag where you can reach it at security.
4. Pre-pay for checked bags online, since airport bag fees are almost always higher.
5. Weigh checked bags at home if you are near the limit, especially on international routes.

Frequently Asked Questions

How many ounces can you carry on a plane?

In the US, containers of liquid, aerosol, gel, cream, or paste must be 3.4 ounces (100 ml) or less, and must fit in a single 1-quart clear bag — one bag per passenger. The limit applies to the container size, not how full it is. Prescription medication, baby formula, and breast milk are exempt and can exceed that amount.

What is the standard carry-on bag size?

Roughly 22 x 14 x 9 inches is common among major US airlines, but it is not universal — some airlines, especially budget carriers, use smaller limits or charge for a full-size carry-on. Always check your specific airline before packing.

What size can checked luggage be?

Checked bags are measured by linear dimensions — length plus width plus height. The common maximum is 62 linear inches (158 cm), which is roughly a 27 x 21 x 14 inch bag. Anything larger is usually treated as oversize and charged accordingly.

Does Basic Economy include a carry-on bag?

Often not a full-size one. Many Basic Economy fares on major US airlines include only a personal item that fits under the seat, with a standard carry-on requiring an upgrade or incurring a gate-check fee.

How much does a checked bag cost?

It varies significantly by airline, route, and how you pay — paying online in advance is typically cheaper than paying at the airport. Compare this cost as part of your total fare, not as an afterthought.

What is the weight limit for a checked bag?

Commonly around 50 lbs (23 kg) on domestic flights and many international economy fares, with some international premium cabins allowing 70 lbs (32 kg). Overweight fees are steep, so weigh your bag at home if you are close to the limit.

Can I bring medication or baby formula over 3.4 ounces?

Yes. Medically necessary liquids and baby formula, breast milk, and juice are allowed in larger quantities. Declare them to the security officer at the checkpoint — they may be screened separately, but they are not subject to the 3.4 oz limit.

Bag fees are where a cheap fare stops being cheap — our flight true cost calculator works out the total across two options once bags and seat fees are included.