TSA 3-1-1 Liquids Rule (Screening Protocols)
The 3-1-1 rule limits ordinary carry-on liquids, gels, aerosols, creams, and pastes to containers holding no more than 3.4 U.S. fluid ounces (100 mL) each. All containers must fit in one clear, resealable, quart-sized bag per passenger. The container’s capacity matters, not the amount left inside. Medical and specified child-feeding items may be exceptions, but still require screening.
A common mistake is packing a nearly empty shampoo bottle that is marked for 200 mL. It may look like it contains less than the limit, but its stated capacity is too large for the ordinary carry-on rule. That can mean repacking or resolving the item at the checkpoint.
I recommend checking the container label before you pack, rather than judging by appearance. The steps below explain what counts, how to pack, and what to expect when you reach screening.
What the 3-1-1 rule means
The rule is a simple way to remember the limits for ordinary liquids in carry-on baggage: containers of 3.4 U.S. fluid ounces (100 mL) or less, packed together in one quart-sized bag, with one such bag per passenger. It covers more than pourable liquids, so check gels, creams, and pastes too.
- 3 means each container has a capacity of 3.4 U.S. fluid ounces (100 mL) or less.
- 1 means the containers fit in one clear, resealable, quart-sized bag.
- 1 means one such bag per passenger for ordinary liquids.
TSA describes this as its liquids rule. A separate federal requirement, 49 CFR § 1540.107, requires passengers to comply with screening instructions. It is not the source of the specific 3-1-1 measurements. At the checkpoint, follow posted directions and the screening officer’s instructions.
Which items count as liquids?
For this rule, the category includes liquids, gels, aerosols, creams, and pastes. Common examples include shampoo, toothpaste, lotion, sunscreen, hair gel, liquid makeup, and spray deodorant. A product’s everyday name or packaging does not decide the matter; its form does.
If you are unsure whether a personal-care product counts, pack it with your liquids. This is a cautious planning step, not a guarantee that every product will be treated the same way. Screening officers make decisions at the checkpoint.
How to pack liquids step by step
Good packing starts at home. Check product types and container capacity, group qualifying items in the required bag, and keep any items that may need separate screening easy to reach.
1. Check each container’s capacity
Look for the amount printed on the bottle, tube, or other container. It must be rated at 100 mL or 3.4 U.S. fluid ounces or less. The limit is based on container capacity, not the quantity of product remaining.
A half-full 150 mL bottle does not meet the ordinary limit. Moving some of its contents into a smaller, clearly sized travel container may be an option, provided the smaller container itself is within the limit.
2. Pack one quart-sized bag
Place the qualifying containers in one clear, resealable, quart-sized bag. TSA guidance does not set one universal bag measurement in inches, so use a bag sold or labeled as quart-sized rather than relying on a guessed dimension.
The bag must be able to close. If it cannot, reduce the number of items or use smaller containers. Do not plan on using a second bag for ordinary liquids; the allowance is one per passenger.
3. Keep exceptions accessible
Keep medically necessary liquids and specified infant or child-feeding items separate from the ordinary liquids bag when practical. Tell the officer about these items before screening so they can be handled as directed.
An exception does not mean an item skips inspection. Screening procedures may differ by checkpoint and equipment, so be ready to follow instructions about presenting the item or undergoing additional screening.
4. Present items as directed
Some lanes or checkpoints may ask you to remove the liquids bag; others may give different instructions. Check signs and listen to the officer. Keep the bag accessible so you can present it without unpacking your whole carry-on.
| Packing question | Ordinary rule | Practical check |
|---|---|---|
| Container size | 100 mL / 3.4 fl oz or less | Read the capacity marking |
| Amount remaining | Does not change the limit | Do not rely on a partly empty larger bottle |
| Bag | One clear, resealable, quart-sized bag | Make sure it closes |
| Number of bags | One per passenger for ordinary liquids | Combine your qualifying items |
| Medical or child-feeding items | May exceed the ordinary limit | Declare them and follow screening instructions |
Exceptions and special items
Some liquids may be allowed in carry-on baggage beyond the ordinary container limit. TSA guidance includes medically necessary liquids and specified infant and child-feeding items. These items still need to be screened, and passengers should tell the officer about them.
Medically necessary liquids
TSA allows medically necessary liquids in reasonable quantities for the trip. Keep them accessible and tell the officer they are medically necessary. The officer may need to screen them separately, so allow time for that process.
Do not assume that a medical label or prescription means the item bypasses screening. The checkpoint officer will explain how to present it. If you have a concern about a particular item, check current TSA guidance before travel.
Infant and child-feeding items
Specified items used to feed an infant or child may be allowed in quantities beyond the ordinary limit. Tell the officer about them at the start of screening and follow directions for separate inspection.
The exception is not a blanket allowance for every liquid carried by an adult traveling with a child. Check TSA’s current guidance to confirm whether a particular item qualifies.
Common packing scenarios
These examples apply the stated limits to familiar situations. They are planning scenarios, not reports of specific checkpoint outcomes; officers may give instructions based on the item and the screening lane.
| Scenario | How to assess it | Next step |
|---|---|---|
| A 100 mL lotion bottle | At the stated maximum for an ordinary container | Put it in the quart-sized bag |
| A 150 mL shampoo bottle with little left | Over the container-capacity limit | Use a compliant smaller container, check it, or leave it behind |
| Several small toothpaste tubes | Each must meet the capacity limit, and all must fit in the one bag | Pack only what fits while allowing the bag to close |
| Liquid medicine above 100 mL | May qualify as medically necessary | Keep accessible, declare it, and follow screening directions |
| A spray toiletry | Aerosols are covered by the liquids rule | Check its container capacity and pack it with ordinary liquids if eligible |
If an ordinary item exceeds the limit and no exception applies, do not count on being able to take it through screening. Before you reach the checkpoint, move it to checked baggage if appropriate, dispose of it, or make another lawful arrangement.
Why screening instructions can differ
The 3-1-1 limits set the basic packing rule, but the way you present items can depend on the checkpoint and its equipment. TSA directs passengers to follow the signs and instructions in their lane. A process you experienced at one airport may not be the process used at another.
This is why the most reliable approach is to pack the liquids bag where you can reach it, then wait for directions before removing it. Avoid assuming that a previous trip determines what an officer will ask you to do this time.
A final pre-checkpoint review
Before leaving for the airport, I use this short check to catch the most common packing errors:
- Identify liquids, gels, aerosols, creams, and pastes.
- Confirm each ordinary container is marked or rated at 100 mL / 3.4 U.S. fluid ounces or less.
- Put ordinary containers in one clear, resealable, quart-sized bag per passenger.
- Keep medical or specified child-feeding items accessible and ready to declare.
- Decide what to do with any oversized ordinary container before reaching screening.
- At the checkpoint, follow the lane’s signs and the officer’s instructions.
The key distinction is capacity, not how full the bottle looks. Check that first, then confirm the bag limit and be ready to present items as directed.
Frequently asked questions
Can I bring a half-full bottle larger than 100 mL?
Not as an ordinary carry-on liquid under the 3-1-1 rule. The container’s capacity, not the amount left inside, controls.
Does the 100 mL limit mean 100 U.S. fluid ounces?
No. The limit is 100 milliliters, which is about 3.4 U.S. fluid ounces.
How many quart-sized bags can I bring?
The ordinary allowance is one clear, resealable, quart-sized bag per passenger.
Do all liquids need to be in the bag?
Ordinary liquids, gels, aerosols, creams, and pastes should fit in that bag. Qualifying medical and child-feeding items may be handled separately; tell the officer about them.
Does toothpaste count as a liquid?
Toothpaste is a paste and is covered by the rule. Use a container of 100 mL / 3.4 U.S. fluid ounces or less and pack it in the bag.
Can I bring liquid medicine in a larger container?
Medically necessary liquids may exceed the ordinary limit. Declare the item and follow the officer’s screening instructions.
Can I bring more than 100 mL of infant formula or another feeding item?
Specified infant and child-feeding items may qualify for an exception. Tell the officer and check current TSA guidance for the item you plan to carry.
Do I have to remove the liquids bag at every checkpoint?
Not necessarily. Procedures can vary by checkpoint and equipment. Follow that lane’s signs and the officer’s instructions.
What if my bag will not close?
Remove items until it closes, or move suitable items to checked baggage. Do not rely on a second bag for ordinary liquids.
What happens if an ordinary container is too large?
If no exception applies, arrange another option before screening, such as placing it in checked baggage or disposing of it.
(This article was written by one of our staff writers, Steven Langford. Visit our Meet the Team page.)
