The 3.4-ounce rule for carry-on liquids

You can bring liquids, gels, and aerosols through TSA security in your carry-on bag only if each container holds 3.4 ounces (100 milliliters) or less. This is the maximum size allowed per item. The rule applies to the container itself, not what's inside it — an empty 3.4-ounce bottle counts the same as a full one.

All your liquid containers must fit into a single quart-sized clear plastic bag. You remove this bag at security and place it in the bin with your shoes and electronics. If even one container exceeds 3.4 ounces, the entire bag may be confiscated.

Liquids in checked baggage have no size limit, so you can pack full-sized bottles, jars, and tubes below the deck. However, some liquids — like certain aerosols and flammables — are forbidden in checked bags entirely, regardless of size.

Key Takeaways

  • Each liquid container in your carry-on must be 3.4 ounces (100 ml) or smaller, and all containers together must fit in one quart-sized clear bag.
  • The 3.4-ounce limit applies to the container size, not the amount of product inside, so a half-empty 3.4-ounce bottle is allowed.
  • Liquids in checked baggage have no size restriction, but some products like certain aerosols and flammables cannot go in checked bags at all.
  • Common items that count as liquids include shampoo, conditioner, lotion, toothpaste, peanut butter, yogurt, and spray deodorant.
  • TSA officers make the final decision at security, and they may confiscate containers that appear to exceed the limit or bags that don't fit the quart-sized requirement.

What counts as a liquid under TSA rules

TSA defines liquids broadly to include anything that flows, spreads, or sprays. This covers obvious items like water, juice, and shampoo, but also thick pastes and gels. Toothpaste, peanut butter, hummus, yogurt, and hair gel all count as liquids under the 3.4-ounce rule.

Aerosols — anything in a pressurized spray can — are treated as liquids. This includes deodorant, hairspray, sunscreen spray, and insect repellent. Solid items like lipstick, solid deodorant, and bar soap do not count and have no size limit in carry-on bags.

If you are unsure whether a product is a liquid, the safest approach is to pack it in your checked bag or buy it after you pass security. TSA officers have final say at the checkpoint, and their judgment can vary slightly between airports.

Converting ounces to milliliters for your bottles

The TSA limit is stated as both 3.4 ounces and 100 milliliters. These are equivalent — 3.4 fluid ounces equals approximately 100 ml. If a bottle says 100 ml or less, it meets the carry-on requirement. If it says 3.4 fl oz or less, it also meets the requirement.

Bottles labeled in metric units (ml or liters) are common in many countries. A 100 ml bottle is the standard travel size and will pass through security. A 200 ml bottle will not. If your bottle is labeled in both units, check the smaller number to be safe — some manufacturers round differently.

When buying travel-sized products, look for labels that specifically say "100 ml" or "3.4 fl oz" or smaller. Many drugstores sell pre-made travel kits with bottles already sized to meet TSA rules.

Packing your liquids bag correctly

Purchase a clear, quart-sized plastic bag — the kind used for freezing food works, or you can buy TSA-approved bags at most airports and drugstores. Place all your liquid containers inside this single bag, then seal it. The entire bag, not individual containers, must fit easily into the bin at security.

Arrange bottles so they do not leak onto each other. If a bottle cap is loose or a container is damaged, wrap it in a plastic bag within the larger bag. Toothpaste and other thick products should be capped tightly. Aerosol cans should have their caps on.

Remove your liquids bag from your carry-on before you reach the security line. When the officer asks, hand them the sealed bag along with your shoes and electronics. Do not open it unless asked — TSA will inspect it if needed.

What happens if your container is too large

If a single container exceeds 3.4 ounces, TSA officers will not allow it through security in your carry-on. You have three options: place it in your checked bag if it is permitted there, throw it away, or leave it with a friend or family member outside security.

Some travelers buy full-sized bottles and pack them in checked luggage, then purchase travel sizes at their destination or at airport shops after passing security. This works well for items like shampoo and lotion, which are widely available in small sizes.

If you are traveling with a medication or medical liquid that exceeds 3.4 ounces, inform the TSA officer before screening begins. Medically necessary liquids may be allowed in larger quantities, but you must declare them and may be asked to open the container for inspection.

International flights and different rules

The 3.4-ounce rule applies to flights departing from the United States, regardless of destination. If you are flying from another country, that country's security rules may differ. The European Union, for example, uses the same 100 ml limit, but other regions may have different restrictions.

If you are connecting through a U.S. airport on an international journey, you must follow TSA rules for the U.S. leg. If you buy liquids at a duty-free shop after passing security at a U.S. airport, you can carry them onto your next flight as long as they are in a sealed duty-free bag.

When traveling internationally, research the security rules for each country you will pass through. Some airports are stricter about what counts as a liquid or how containers are measured.

Common mistakes to avoid at security

The most common error is packing liquids in a regular bag instead of a clear quart-sized bag. TSA will ask you to remove them, which slows your line and may result in confiscation if you cannot produce the correct bag quickly.

Another mistake is forgetting that you already have liquids in your carry-on from a previous trip. Check your bag before packing new items — old sunscreen, lotion, or shampoo left from a past flight can push you over the limit.

Do not assume a container is under 3.4 ounces based on how full it looks. A half-empty 5-ounce bottle is still too large. Check the label on the container itself, not the amount of product inside.

Frequently Asked Questions

Can I bring a full water bottle through security?

No. Water is a liquid and must follow the 3.4-ounce rule. You can bring an empty water bottle through security and fill it at a fountain or water station on the other side. Many airports have refill stations near gates.

Do solid deodorant and lipstick count as liquids?

No. Solid deodorant, lipstick, and other solid products are not restricted by the 3.4-ounce rule. Only aerosol deodorant (spray cans) counts as a liquid. You can pack solid items in any size in your carry-on.

What if my medication is a liquid and exceeds 3.4 ounces?

Tell the TSA officer before screening that you are carrying a medically necessary liquid. Prescription medications and other medical liquids may be allowed in larger quantities, though the officer may open and inspect the container. Have your prescription label or documentation ready.

Can I pack liquids in my checked bag without a size limit?

Yes, liquids in checked baggage have no size restriction. However, some products — like certain aerosols, flammables, and oxidizers — are forbidden in checked bags entirely. Check TSA.gov or ask at the ticket counter if you are unsure about a specific item.

What if my bottle says 100 ml but looks larger than other 3.4-ounce bottles?

Trust the label, not the appearance. Bottles vary in shape and width, so a 100 ml bottle may look taller or wider than another 100 ml bottle. As long as the label says 100 ml or 3.4 fl oz or less, it meets the requirement.