At US airport security, liquids, aerosols, gels, creams and pastes in your carry-on must be in containers of 3.4 ounces (100 milliliters) or less, and they must all fit in one quart-sized bag. Anything in a bigger container goes in your checked bag. There are three main exceptions: medically necessary liquids, baby formula, breast milk and baby food, and duty-free liquids bought abroad in a sealed security bag when you connect to a US flight. Rules outside the US are now less uniform, because some UK and European airports with new scanners allow larger containers.
What 3-1-1 means
- 3.4 ounces (100 ml) or less per container. The container size counts, not how much is left in it: a half-empty 6-ounce bottle of sunscreen is still too big.
- 1 quart-sized bag, clear and resealable, holding all those containers.
- 1 bag per passenger.
In a standard lane you take the bag out and put it in a bin on its own. With TSA PreCheck you can usually leave it in your carry-on, but the size limit still applies. Anything that alarms during screening gets a closer look, which is where most security delays come from.
What counts as a liquid
TSA's rule covers more than drinks. Treat anything you can spread, squeeze, spray or pour as a liquid: toothpaste, shampoo, lotion, sunscreen, hair gel, mascara, liquid foundation, perfume, hand sanitizer, peanut butter, hummus, yogurt, dips and jam. Solid items such as stick deodorant, bar soap, solid shampoo bars and lipstick are not limited. If you are unsure about a specific item, TSA's "What Can I Bring?" tool on tsa.gov gives a yes or no.
Exception 1: Medicines
TSA allows larger amounts of medically necessary liquids, gels and aerosols "in reasonable quantities for your trip." They do not need to fit in the quart bag. You must tell the officer at the start of screening and take them out to be screened separately, and the officer may test them. That includes things like liquid prescriptions and gel packs that keep medicine cool. For carrying prescriptions abroad, and foreign rules that can be stricter, see our guide to flying with medication.
Exception 2: Baby formula, breast milk and baby food
TSA treats formula, breast milk, toddler drinks and baby or toddler food, including puree pouches, as medically necessary liquids. Larger quantities are allowed in your carry-on and do not need to go in the quart bag. The same goes for ice packs, freezer packs and gel packs that keep them cold, with or without milk in them. Your child does not have to be traveling with you.
Tell the officer at the start that you have these items over 3.4 ounces and take them out for separate screening. TSA suggests clear bottles rather than bags or pouches, since pouches may need to be opened for other tests. Our guide to flying with a baby covers the rest of the trip.
Exception 3: Duty-free liquids on a connection into the US
This catches many travelers on the way home. You buy perfume or a bottle of liquor at the airport abroad, land in the US, and then have to go through TSA security again for your connecting flight. TSA lets you carry duty-free liquids over 3.4 ounces through that checkpoint only if all of these are true:
- You bought them internationally and are flying to the US with a connecting flight.
- The retailer packed them in a transparent, secure, tamper-evident bag (often called a STEB), and the bag shows no sign of being opened.
- You have the original receipt, and you bought them within 48 hours.
- The items clear screening. Anything that alarms or cannot be screened is not allowed in your carry-on.
TSA itself recommends putting duty-free liquids over 3.4 ounces in your checked bag, even when they are sealed. The easy moment to do that is right after US customs, when you collect your bags and re-check them for the connection: open your suitcase and pack the bottle before you hand it back. If you opened the security bag on the plane, it no longer qualifies.
Rules abroad are changing: check each airport
The 100 ml limit is used widely around the world, but the UK and the European Union are moving away from it airport by airport as new CT scanners arrive. These scanners can screen larger containers and let you keep liquids and laptops in your bag.
- European Union: the EU reinstated the 100 ml limit at airports with these scanners in September 2024 for technical reasons. In July 2025 European regulators approved updated scanner software, and airports with approved equipment were allowed to accept containers of up to 2 liters. Not every airport has the equipment, and some use it only in certain lanes.
- United Kingdom: the UK government says the rules for liquids "have changed at some UK airports" and tells travelers to check with the airport before they fly.
The practical rule: the strictest airport on your trip decides. A 2-liter bottle that passed security at one European airport can be confiscated when you connect at another airport that still screens at 100 ml, and it will not pass a US checkpoint on a connection home. If you want to travel carry-on only, pack to 3.4 ounces and you are covered everywhere. Our carry-on packing guide shows how.
Packing tips that save time at security
- Use travel bottles that are clearly marked 100 ml or 3.4 oz. Unmarked bottles invite questions.
- Switch to solids where you can: shampoo bars, stick sunscreen, solid perfume.
- Pack your quart bag last, at the top of your carry-on, so it comes out in one move.
- Bring an empty water bottle and fill it after security.
- Remember batteries too: spare lithium batteries and power banks must be in your carry-on, not your checked bag. See our power bank rules.
