TSA Liquid Rules for Carry-On Bags (3-1-1 Rule Explained)

The Transportation Security Administration's liquid rule is one of the most misunderstood security requirements in air travel. Implemented in 2006 following a foiled liquid-explosive plot in the UK, the rule has been in place for nearly two decades — but travelers still regularly lose toiletries, drinks, and food items at the checkpoint because of it.

This guide explains exactly what the rule means, what counts as a liquid, which items are exempt, and how to pack your carry-on to breeze through security.

What the 3-1-1 Rule Means

The rule is named for its three key numbers:

3.4 oz (100 ml) — the maximum size of any individual liquid container you can bring through security in your carry-on.

1 quart-sized bag — all your liquid containers must fit together inside a single, clear, zip-top plastic bag that is approximately one quart (roughly 1 litre) in volume. A standard sandwich-size zip-lock bag is too small; a quart-size bag is about 17 cm × 20 cm.

1 bag per person — each passenger is allowed one quart-sized bag of liquids. You cannot pool two people's liquids into one bag.

At the security checkpoint, you must remove this bag from your carry-on and place it separately in a screening bin. This is the step most travelers forget, leading to additional screening and delays.

What Counts as a Liquid?

The TSA defines "liquids" broadly. The rule applies to:

• Liquids — water, juice, coffee, alcohol, soup, sauces, dressings
• Gels — toothpaste, hair gel, face moisturizer, body lotion, aloe vera gel
• Aerosols — hairspray, deodorant spray, cooking spray, spray sunscreen
• Creams and pastes — foundation, mascara, peanut butter, hummus, jam
• Suspensions — snow globes, liquid glitter items

If you're unsure whether something counts, ask yourself: could it be used as a liquid or gel, even if it has a semi-solid consistency? If yes, it's subject to the rule. Peanut butter is a gel. Spreadable cheese is a gel. Mascara is a liquid.

What Does NOT Count as a Liquid

• Solid food (sandwiches, fruit, cheese blocks, chocolate bars, hard candy)
• Solid deodorant (not gel or spray)
• Solid sunscreen sticks
• Powder (dry shampoo powder, baby powder, protein powder — though powders over 350 ml in containers now receive additional screening)
• Lip balm (solid stick form)
• Solid makeup (compact powder, blush, eye shadow)

When in doubt, a good rule: if it pours, pumps, sprays, or squeezes, it's a liquid under the TSA's definition.

The 100 ml Container Limit

The limit applies to container size, not content. A 200 ml bottle that is half-empty is not allowed through security — the container itself must be 100 ml or smaller.

This means:

• A 100 ml bottle filled to the brim: allowed
• A 500 ml bottle that's 80% empty: not allowed
• A 3.4 oz (100 ml) travel-size shampoo: allowed
• A full-size 250 ml conditioner: not allowed, even if you only packed it because it was 40% full

Transfer your products to travel-size containers (available at pharmacies and travel stores) before leaving home.

The Quart-Sized Bag Requirement

All your 100 ml containers must fit together inside a single transparent, resealable bag approximately one quart (946 ml) in volume. The bag must:

• Be clear (transparent) — not opaque or tinted
• Be resealable (zip-top) — not a twist-top or open bag
• Contain only your liquids — it goes in its own bin, separate from your carry-on

One quart-sized bag holds approximately 8–10 travel-size containers (100 ml each) when packed efficiently. If you can't close the bag, you have too many items.

You can purchase designated TSA-approved liquid bags, but any clear zip-top quart-sized bag (like a standard Ziploc freezer bag in the quart size) works fine. TSA does not require a particular brand.

Exemptions: What Doesn't Follow the 3-1-1 Rule

Several categories of liquids are explicitly exempt from the 100 ml rule. They still must be declared separately at the checkpoint and will receive additional screening, but they can be in quantities greater than 100 ml.

Medically Necessary Liquids

Prescription medications, over-the-counter medications, vitamins, and medical devices containing liquids (insulin vials, liquid nutritional supplements, eye drops for documented medical conditions) are exempt. You must:

1. Declare them verbally to the TSA officer at the checkpoint.
2. Remove them from your bag and place them in a bin for separate screening.
3. Be prepared for additional screening questions.

You do not need to carry a prescription or doctor's note, but having pharmacy labeling or a letter from your physician speeds up the process significantly for large quantities.

Baby Formula, Breast Milk, and Juice for Infants

Baby formula, expressed breast milk, and juice for infants and toddlers are exempt in reasonable quantities. "Reasonable" is not defined numerically — the TSA officer has discretion, but enough formula for the flight plus some buffer is generally accepted without issue. As with medications, declare these separately at the checkpoint.

Ice packs used to keep breast milk cold are also permitted if they are still frozen or slushy. If they are partially melted (liquid), they are subject to the 100 ml rule.

Duty-Free Liquids Purchased at the Airport

Liquids purchased airside (after clearing security) in an airport duty-free shop may be carried in quantities larger than 100 ml in a tamper-evident duty-free bag. If you are making a connection and will need to pass through security again, check whether your connecting airport accepts sealed duty-free bags — rules vary internationally.

Practical Packing Tips

Build a dedicated liquid kit. Keep a pre-assembled quart-size bag with your travel toiletries — mini shampoo, conditioner, toothpaste, face wash, sunscreen, and hand lotion — ready to go. Repack and replace items as they run out. This saves repacking time before every trip.

Use refillable travel bottles. Rather than buying travel sizes each trip, invest in a set of refillable silicone bottles (100 ml or less). Label them with a marker or label tape so you're not opening each one to remember what's inside.

Pack solid alternatives. Solid shampoo bars, conditioner bars, solid sunscreen sticks, and solid deodorant are not subject to the liquid rule and save quart-bag space for items that have no solid equivalent (prescription liquid medications, contact lens solution).

Put the liquid bag on top. Pack your quart bag last so it's accessible at the top of your carry-on when you approach the security checkpoint. Rooting through a packed bag at the belt wastes time and creates stress.

Don't rely on "consuming it before the checkpoint." TSA lines move unpredictably. A full water bottle you planned to drink in the queue may still be full when you reach the X-ray. Either finish it well before security or surrender it.

Know your connecting airports. If you're flying from the US to Europe via a hub, you'll clear security once in the US and may clear again in the hub. European airports use the same 100 ml standard but enforce it independently. Don't assume a duty-free purchase in one country clears security in another.

International Airports and Liquid Rules

Most international airports follow the International Civil Aviation Organization (ICAO) standard, which is effectively the same as the TSA rule: 100 ml containers in a 1-litre transparent bag. This covers all EU airports, UK airports, Canadian airports, Australian airports, and most major Asian hubs.

Notable differences:

• Some airports allow liquids in a slightly larger bag (up to 1 litre rather than exactly 1 quart).
• Enforcement tolerance varies — some airports are more lenient than others.
• Airport security screening in many countries does not require you to remove shoes, which changes the flow of the bin process but not the liquid rule.

If you're travelling internationally, always verify the rules for each airport you'll pass through, as local variations occasionally exist.