If you are flying from a United States airport with a carry-on bag, the TSA 3-1-1 rule decides how you pack your liquids, gels, and aerosols. In short, each container must hold 3.4 ounces (100 milliliters) or less, all of those containers must fit inside one quart-sized bag, and each passenger is allowed one bag. Anything larger belongs in checked luggage, unless it falls under a limited exception, such as medically necessary liquids or baby formula. Once you understand what each number means, packing takes only a few minutes.
What The TSA 3-1-1 Rule Means
The name “3-1-1” is a memory aid, and each number stands for one part of the rule. The TSA states it this way: you may bring a quart-sized bag of liquids, aerosols, gels, creams, and pastes in your carry-on bag and through the checkpoint, limited to travel-sized containers of 3.4 ounces (100 milliliters) or less per item. The TSA’s frequently asked questions page adds that each passenger is limited to one quart-size bag. The rule applies to carry-on baggage at United States airport checkpoints, not to checked luggage.
The First Number: 3.4 Ounces Or Less Per Container
The “3” in 3-1-1 refers to 3.4 ounces, or 100 milliliters, the largest size allowed for any single container in your carry-on liquids bag. This limit is about the size of the container itself, not how much product is left inside it. A large bottle that is nearly empty still breaks the rule if the container is labeled larger than 3.4 ounces. To bring a favorite shampoo, lotion, or sunscreen, pour some into a travel-sized container of 3.4 ounces or smaller, or buy a travel-sized version before your trip. Always check the label before you pack, because officers judge the container, not the amount remaining.
The Second Number: One Quart-Sized Bag
The first “1” in 3-1-1 refers to one quart-sized bag. Every liquid, gel, aerosol, cream, and paste container in your carry-on must fit inside that single bag, and the bag must close. A standard clear, resealable, quart-sized zip-top bag lets officers see the contents during screening. A gallon-sized bag or a large toiletry pouch does not meet the rule, even if it holds only small containers. If your containers do not all fit with the bag closed, you have packed too much for a carry-on, and the extra items should go in checked luggage or stay home.
The Third Number: One Bag Per Passenger
The second “1” in 3-1-1 refers to one bag per passenger. Each traveler is limited to one quart-sized bag of liquids, gels, and aerosols. You cannot spread your toiletries across two bags for yourself. Pack each person’s liquids separately to avoid confusion when bags are screened.
What Counts As A Liquid, Gel, Or Aerosol
The rule covers more than water and juice. It applies to liquids, aerosols, gels, creams, and pastes, which means many everyday toiletries count. The TSA lists toothpaste, shampoo, conditioner, mouthwash, and lotion among the common travel items that must comply. Beyond those, the same limit covers liquid soap, sunscreen, hair gel, gel or spray deodorant, perfume, liquid foundation, lip gloss, and shaving cream. A useful test is whether the item pours, squeezes, sprays, or spreads. If it does, put it in your quart-sized bag. Solid items, such as a bar of soap or solid deodorant, are generally handled differently. If you are unsure about a product, the TSA’s “What Can I Bring?” tool on TSA.gov can confirm how it is treated before you pack.
Items That Often Surprise Travelers
Some items catch travelers off guard because they do not look like liquids at first glance. The following items all fall under the 3-1-1 rule in a carry-on bag:
- Peanut butter, jam, and other spreads, which are gels and pastes
- Yogurt, pudding, and dips, treated as liquids and gels
- Liquid or gel medications above the limit, only when they qualify for the medical exception below
- Aerosol sprays, including hairspray and spray sunscreen
- Creamy cosmetics, such as liquid foundation and cream blush
- Contact lens solution in a standard-sized bottle, unless declared as a medically necessary liquid
Foods that are clearly solid, such as a sandwich or a granola bar, are a different matter, but anything spreadable, pourable, or squeezable should go in the liquids bag. When in doubt, put the item in the bag or in checked luggage rather than hoping an officer will make an exception.
Exceptions To The TSA 3-1-1 Rule
The rule has a small number of exceptions, and each one comes with its own process. An exception does not mean you can carry a large bottle through without telling anyone. In each case below, inform the TSA officer and be ready for separate screening.
Medications And Medically Necessary Liquids
The TSA allows larger amounts of medically necessary liquids, gels, and aerosols in reasonable quantities for your trip. This covers liquid prescription medication and other liquids you genuinely need for a medical reason during travel. These items do not have to fit in your quart-sized bag, but you must declare them to a TSA officer at the checkpoint, and they will be screened separately. Keep them easy to reach so you can present them without unpacking your whole bag. Bring what you need for the journey, not a bulk supply, and check TSA.gov if you are carrying anything unusual, such as supplies connected to a medical device.
Baby Formula, Breast Milk, And Baby Food
Formula, breast milk, and juice for infants and toddlers are allowed in quantities greater than 3.4 ounces in carry-on baggage, and they do not need to fit in the quart-sized bag. The TSA also allows baby food, including purees. These items are removed from your bag for separate screening, so tell the officer at the start of screening and keep them accessible. Ice packs, freezer packs, and gel packs used to keep formula or breast milk cold are also allowed. According to the TSA, you do not need to be traveling with a child to bring breast milk through the checkpoint. Allow extra time, because separate screening takes longer than the standard process.
Duty-Free Purchases On International Trips
Liquids bought at a duty-free shop abroad may be allowed through a connecting checkpoint in the United States in sizes larger than 3.4 ounces, but only under strict conditions. The purchase must be sealed by the retailer in a tamper-evident bag, and you should keep the original receipt. Because the details matter and can change, check the TSA’s current duty-free guidance on TSA.gov before relying on this exception, and do not open the sealed bag before you clear security.
How To Pack Your Liquids Bag Like A Regular Traveler
Packing well takes a few minutes at home and saves a much longer wait at the airport. A simple routine works for most trips:
- Buy quart-sized, clear, resealable zip-top bags and keep one in your travel kit
- Decant favorite products into labeled travel containers of 3.4 ounces or less
- Put the liquids bag at the top of your carry-on so you can take it out quickly if asked
- Tighten every cap, and place the bag inside a small pouch so a leak cannot reach your clothes
- Keep medications and baby items separate from the quart bag, easy to reach, and ready to declare
- Pack full-sized bottles in checked luggage, and carry only what you need for the flight and the first day
If you travel often, keep a ready-packed liquids bag at home and refresh it after each trip.
Common Mistakes That Slow You Down
Most checkpoint delays involving liquids come from a handful of avoidable mistakes:
- Bringing a container larger than 3.4 ounces because it is almost empty; the rule measures the container, not what is left inside
- Using a bag bigger than quart-sized, or a toiletry pouch that cannot be seen through
- Packing liquids loose throughout the carry-on instead of together in one bag
- Forgetting to declare medications or baby formula and breast milk
- Assuming the rules at a foreign airport are the same as the TSA rules
- Waiting until the checkpoint to deal with an oversized bottle, when the only options are to surrender it or return to check it
A quick check before you leave home solves nearly all of these. Lay out everything you plan to carry on, confirm each container is 3.4 ounces or smaller, confirm everything fits in one quart-sized bag that closes, and set aside anything that does not fit for checked luggage.
What Happens If You Break The Rule
If an officer finds a container larger than 3.4 ounces or a bag that does not meet the rule, you will usually face an inconvenient choice. You may be asked to surrender the item, which means it is thrown away. You may be able to leave the checkpoint, put the item in checked luggage, and return through screening, but that only works if you have time before your flight and your airline can still accept the bag. In some cases you may be able to hand the item to someone who is not traveling, but never count on that option. The final decision at the checkpoint rests with the TSA officer, so solve packing problems at home, not at the checkpoint.
Frequently Asked Questions About The TSA 3-1-1 Rule
Can I Bring A Water Bottle Through Security If It Is Empty?
Yes. An empty reusable water bottle can go through the checkpoint, because there is no liquid in it to measure, and you can fill it at a refill station after screening. A bottle that still contains water or juice is treated as a liquid and must follow the 3-1-1 rule, which means a standard bottle of water will not pass.
Does The 3-1-1 Rule Apply To Children And Infants?
Yes, the rule applies to each passenger, but the exceptions for baby formula, breast milk, juice, and baby food mean parents and caregivers can carry what an infant or toddler needs in larger quantities. Those items must be declared and screened separately. Older children with their own carry-on are each limited to one quart-sized bag, just like adults.
Can I Bring Sunscreen And Insect Repellent In My Carry-On?
Yes, as long as each container is 3.4 ounces or less and fits in your quart-sized bag. If you need a larger amount, pack the full-sized bottle in checked luggage and carry a travel-sized container for the flight and the first day.
What Should I Do If I Am Unsure Whether An Item Counts?
Use the TSA’s “What Can I Bring?” tool on TSA.gov and search for the item by name before you pack. If you still cannot find a clear answer, pack it in checked luggage or leave it behind. Guessing at the checkpoint risks losing the item and delaying your screening.
Do The Same Liquid Limits Apply When I Fly Home From Another Country?
Not necessarily. Other countries set their own aviation security rules, and while many use a similar 100-milliliter limit, the details, bag requirements, and exceptions can differ. Always check the rules of the country you are departing from, and of any country where you connect, before your return flight.
Pack Smart And Skip The Checkpoint Stress
The TSA 3-1-1 rule is not complicated once you break it into its three parts: containers of 3.4 ounces or less, one quart-sized bag, and one bag per passenger. Pack your liquids bag at home, keep medications and baby items declared and easy to reach, and put full-sized bottles in checked luggage. Before every trip, check TSA.gov for the latest guidance, because security procedures can change. For travel planning, also confirm the rules at your destination and any connection.
