The liquid limit on airplanes in the United States is 3.4 ounces (100 milliliters) per container for anything you carry on, and every container has to fit inside a single quart-sized clear plastic bag, one bag per passenger. This is the TSA’s 3-1-1 rule, and it applies to every ticket and every destination. Medical liquids, baby formula and breast milk, and sealed duty-free purchases are treated separately. Checked bags follow different rules entirely.
The 3-1-1 Rule in Plain Terms
Three numbers: 3.4-ounce containers, 1 quart-sized bag, 1 bag per passenger. Each container of liquid, gel, aerosol, cream, or paste must hold 3.4 ounces (100 milliliters) or less.1Transportation Security Administration. Liquids, Aerosols, and Gels Rule What matters is the size of the container, not how much liquid is inside. A half-empty 8-ounce shampoo bottle gets taken at the checkpoint even though the shampoo left in it is well under the limit.
Toothpaste, shampoo, conditioner, mouthwash, lotion, hair gel, and spreadable foods like hummus and peanut butter all fall under the rule.2Transportation Security Administration. Liquids, Aerosols, and Gels Rule If you arrive at the checkpoint with something oversized, a TSA officer will ask you to surrender it. Depending on the airport and how much time you have, you can sometimes leave the line and move the item to a checked bag instead.
What Counts as a Liquid
The line between liquid and solid isn’t always intuitive. Gel deodorant and spray deodorant both count as liquids. Stick deodorant does not, and it can go anywhere in your carry-on with no size limit. The same applies to solid lipstick, bar soap, solid perfume, powder makeup, and dry sheet masks.
Wet or creamy cosmetics get treated as liquids. Mascara, liquid foundation, and cream blush all belong in the quart bag. A useful test: if the product would spill when you tip the container, pack it as a liquid.
Drinks and Water After Security
The 3-1-1 rule stops at the checkpoint. Once you’ve cleared screening, you can buy any size drink in the terminal and bring it onto the plane. You can also carry an empty water bottle through security and fill it at a fountain on the other side.3Transportation Security Administration. Empty Water Bottle
Medical Liquids, Baby Formula, and Breast Milk
Baby formula, breast milk, toddler drinks, and baby food (including puree pouches) are allowed in quantities larger than 3.4 ounces, and they don’t have to fit in the quart bag. TSA treats them as medically necessary. Your child doesn’t need to be with you for breast milk or formula to qualify.4Transportation Security Administration. Baby Formula
Ice packs, freezer packs, and gel packs used to cool breast milk or formula are also permitted, whether or not the milk itself is present. Prescription liquid medications and other medically necessary liquids like saline solution get the same allowance. Pull these items out separately at screening so an officer can inspect them, which may include opening containers or running extra tests. A doctor’s note isn’t required, but one can help if you’re carrying an unusual volume.
Duty-Free Purchases and Connecting Flights
Liquids bought at duty-free shops inside the secure area of an airport can be carried onto your flight even if they’re over 3.4 ounces, because you’ve already passed security. The issue is what happens when you connect.
If you bought duty-free liquids at an international airport and are connecting through a U.S. hub, TSA lets you keep them in your carry-on only if the retailer sealed them in a transparent, tamper-evident security bag with the seal still intact. The original receipt has to be visible, and the purchase has to have happened within the previous 48 hours.1Transportation Security Administration. Liquids, Aerosols, and Gels Rule If the seal is broken, the liquid is confiscated or has to move to checked baggage. The cleanest workaround is to pack duty-free liquids in your checked bag from the beginning.
Alcohol Rules by Strength
Alcohol is sorted by alcohol by volume (ABV), and the rules differ between carry-on and checked bags.
In carry-on, mini bottles are allowed if each bottle is 3.4 ounces or less and they all fit inside your quart bag. One catch worth knowing: FAA rules bar you from drinking your own alcohol on the plane. Only drinks the flight crew serves can be consumed during the flight.5Transportation Security Administration. Alcoholic Beverages
In checked luggage, federal rules split alcohol into three tiers:
- 24% ABV or less (most beers and wines): no quantity limit.6eCFR. 49 CFR 175.10 – Exceptions for Passengers, Crewmembers, and Air Operators
- Between 24% and 70% ABV (most spirits): capped at 5 liters per passenger in unopened retail packaging.6eCFR. 49 CFR 175.10 – Exceptions for Passengers, Crewmembers, and Air Operators
- Over 70% ABV (140 proof and above): prohibited in both carry-on and checked baggage.6eCFR. 49 CFR 175.10 – Exceptions for Passengers, Crewmembers, and Air Operators
That top tier catches people out. Some cask-strength whiskeys, overproof rums, and grain alcohols clear 70% ABV and can’t fly at all, in any bag.
Liquids in Checked Bags
Most ordinary liquids like shampoo, water, and non-alcoholic drinks have no volume cap in checked bags. Aerosol toiletries and medicinal products, such as hairspray, perfume, and alcohol-based medicines, are treated as hazardous materials and face tighter limits. Each container is capped at 500 milliliters (17 fluid ounces), and the combined total across all such items cannot exceed 2 liters (68 fluid ounces) per passenger.6eCFR. 49 CFR 175.10 – Exceptions for Passengers, Crewmembers, and Air Operators
Foreign Airports and International Flights
The 100-milliliter container limit isn’t only an American rule. It came out of guidelines set by the International Civil Aviation Organization and has been adopted by aviation authorities worldwide, including the European Union and most countries across Asia, Africa, and South America. Flying out of a foreign airport, expect the same core setup: containers of 100 milliliters or less, packed in a clear resealable bag roughly one liter in size. Minor differences in bag size and screening procedure exist between countries, but the essential limit is nearly identical everywhere.
What Happens if You Break the Rule
Leaving a water bottle in your bag by accident isn’t a legal problem. TSA pulls the item and gives you the choice to surrender it or, if there’s time, walk it back to the check-in counter. Deliberately trying to bring prohibited liquids through security is different. TSA can impose civil penalties of up to $17,062 per violation, with higher fines for repeat offenders.7Transportation Security Administration. Civil Enforcement
Flammable liquids like gasoline, lighter fluid, and paint thinner carry penalties from $450 to $2,570 per incident.7Transportation Security Administration. Civil Enforcement Prohibited items found at the checkpoint, in the secure area, or on board an aircraft can trigger both civil enforcement and criminal prosecution. Honest mistakes get handled routinely. Trying to slip something through can turn expensive quickly.