The 3.4-ounce rule for carry-on bags

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 hard limit — 3.5 ounces will not pass. The rule applies to the size of the container itself, not how full it is, so an empty 3.4-ounce bottle counts toward your limit even if you only put 1 ounce of liquid in it.

All containers must fit into a single quart-sized clear plastic bag. TSA provides no bag, so you bring your own or use one from the security line. One bag per person. If your liquids do not fit in one quart bag, you cannot bring them through security in your carry-on.

Key Takeaways

  • Each liquid container in your carry-on must be 3.4 ounces or smaller, and all containers together must fit in one quart-sized clear bag.
  • Liquids in checked baggage have no size limit per container, but the total weight of your bag cannot exceed the airline's limit, usually 50 pounds.
  • Common liquids that count toward the rule include shampoo, conditioner, lotion, toothpaste, peanut butter, yogurt, and jam — not just water and juice.
  • Frozen liquids are treated as solids at security, but they must stay frozen; if they thaw to liquid form during screening, they become subject to the 3.4-ounce rule.
  • Medications and medical liquids like insulin have different rules and do not need to fit in the quart bag, but you should declare them to TSA officers.

What counts as a liquid under TSA rules

TSA defines liquids broadly. The category includes obvious ones like water, juice, and soda, but also shampoo, conditioner, body lotion, sunscreen, deodorant, toothpaste, mouthwash, and perfume. It also includes foods that are liquid or semi-liquid at room temperature: peanut butter, yogurt, jam, honey, maple syrup, and hummus all count. Solid foods like cheese, chocolate bars, and crackers do not.

Aerosols — spray cans of deodorant, hairspray, or sunscreen — follow the same 3.4-ounce limit. A full-size aerosol can is usually larger than 3.4 ounces and will not pass through security in your carry-on. You can bring travel-size aerosol cans if they are 3.4 ounces or smaller.

Gels like hair gel, aloe vera gel, and contact lens solution count as liquids. Solid stick deodorant does not. If you are unsure whether something is a gel or a solid, assume it is a gel and pack it in your quart bag.

Liquids in checked baggage have no per-container limit

You can pack full-size bottles of shampoo, lotion, sunscreen, and other liquids in your checked bag with no restriction on container size. A 16-ounce bottle of shampoo is fine in checked baggage. The only limit is the total weight of your bag — most airlines allow 50 pounds for a checked bag, some allow 70 pounds.

Checked baggage is screened separately from carry-on bags, and TSA does not explore the 3.4-ounce rule to items below the deck. This is why many travelers pack toiletries in checked bags instead of trying to fit travel sizes in a carry-on.

If you are checking a bag and also carrying on a bag, you can bring full-size liquids in the checked bag and travel-size liquids in the carry-on. This gives you flexibility if you need to use toiletries during your flight or at your destination before your checked bag arrives.

Frozen and partially frozen liquids

A frozen liquid is treated as a solid at security and does not count toward the 3.4-ounce limit. You can bring a frozen water bottle, a frozen gel pack, or a container of frozen yogurt through security in your carry-on. The item must be completely frozen solid when you go through the checkpoint.

If a frozen item begins to thaw during security screening and becomes slushy or liquid, TSA may treat it as a liquid and reject it if it exceeds 3.4 ounces. To be safe, keep frozen items in an insulated bag or ask TSA officers to screen them separately so they stay frozen longer.

Medications, baby formula, and medical liquids

Medications in liquid form — insulin, liquid antibiotics, cough syrup — do not need to fit in your quart bag and are not subject to the 3.4-ounce limit. You can bring any amount of prescription medication in liquid form. Bring the original labeled container so TSA can verify it is medication.

Baby formula, breast milk, and baby food are also exempt from the 3.4-ounce rule. You can bring any amount in your carry-on. You do not need to taste or open the containers for TSA, though officers may ask to screen them separately.

Declare all medications and medical liquids to the TSA officer at the checkpoint before you place your bag on the scanner. This speeds up screening and prevents confusion.

What happens if you try to bring oversized liquids

If a liquid container is larger than 3.4 ounces and does not fit in your quart bag, TSA will not allow it through security in your carry-on. You have three choices: leave it behind, pack it in your checked bag if you have one, or go back to the ticket counter and check your carry-on bag instead.

TSA does not charge a fee for confiscating liquids, but you lose the item. Some travelers intentionally pack liquids they do not mind losing, or they buy toiletries after passing security at airport shops or at their destination.

International flights and other countries' rules

The 3.4-ounce rule applies to flights departing from the United States, regardless of where the flight is going. If you are flying from the US to Europe, Canada, or anywhere else, you follow the US TSA rule through US security.

When you arrive at your destination and connect to another flight, you may face different rules. European airports, for example, follow the same 3.4-ounce rule, but some other countries have different limits. If you are connecting internationally, pack liquids in your checked bag when possible to avoid having to repack at a connection.

Frequently Asked Questions

Can I bring a full water bottle through security?

No. An empty water bottle is fine, but you cannot bring a full or partially full water bottle through security in your carry-on. You can fill it at a water fountain or bottle-filling station after you pass the checkpoint, or buy a bottle of water at an airport shop.

Does toothpaste count as a liquid?

Yes. Toothpaste is a gel and counts toward the 3.4-ounce limit. A standard tube of toothpaste is usually 5 to 6 ounces, so you need a travel-size tube (typically 0.85 to 1.5 ounces) in your carry-on. Full-size tubes can go in checked baggage.

What if my liquid container says 3.4 ounces but looks full?

The size of the container is what matters, not how full it is. If the label says 3.4 ounces or 100 milliliters, it passes. TSA does not measure the liquid inside — they check the container's stated capacity.

Can I bring multiple small bottles that add up to more than 3.4 ounces?

Yes, as long as each individual bottle is 3.4 ounces or smaller and all bottles fit in one quart bag. You could bring ten 3-ounce bottles if they all fit in the bag. The rule is per container, not per total amount.

Do I need to remove my liquids bag at security?

Yes. Place your quart bag on the conveyor belt with your other items, or remove it from your carry-on bag and place it in a bin. TSA will screen it separately. This speeds up the process and reduces the chance of a liquid being flagged.