What is the 100ml liquid rule?

The 100ml rule (used in the EU, UK, Australia, and most countries outside the US) states that any liquid, gel, cream, or paste in your carry-on must be in a container of 100ml or less. All containers must fit in a single transparent, resealable plastic bag of no more than one litre capacity — typically about 20×20 cm.

What counts as a liquid at airport security?

Liquids include anything that flows or can be spread: water, juice, shampoo, conditioner, face wash, moisturiser, sunscreen, toothpaste, mascara, lip gloss, gel deodorant, hair gel, peanut butter, yoghurt, and soft cheeses. If you can squeeze, pour, or spread it, it's treated as a liquid.

Are medications and baby milk exempt from the liquid rule?

Yes. Prescription and over-the-counter medications in liquid form, baby milk (formula and breast milk), and food for infants are exempt from the 100ml limit in most countries. You may need to declare them separately at the security checkpoint and may be asked for evidence (prescription, boarding pass showing an infant, etc.).

Can I bring duty-free liquids in my carry-on?

Yes, with conditions. Duty-free liquids purchased airside (after security) can be brought on board in their original sealed, tamper-evident bag with the receipt visible. On connecting flights, check the rules for your transit country — some countries (including the UK at certain points) have refused duty-free liquids from non-exempt countries at transfer security.

What happens to liquids over 100ml at security?

Security officers will confiscate any liquid in a container over 100ml, even if the container is mostly empty. There is no option to pour the excess out — the entire container is taken. The only exception is medically necessary liquids that have been declared and screened separately.

Liquid Rules for Carry-On Bags: The 100ml Rule Explained

Airport security liquid rules are one of the most misunderstood aspects of air travel. The same toothpaste, moisturiser, or bottle of water that you carry freely in your checked bag becomes contraband in your carry-on if it exceeds certain size limits. This guide explains why the rules exist, exactly what they mean in different countries, and how to pack liquids so you never lose them at the checkpoint again.

Why the Liquid Restriction Exists

The liquid rule was introduced in 2006 following a foiled plot to detonate liquid explosives on transatlantic flights. Security agencies determined that small quantities of liquid posed a manageable risk, while larger quantities did not. The result was an internationally adopted standard: containers of 100ml or less, all contained in a single 1-litre transparent bag.

The rule has been in place for nearly 20 years. Despite advances in airport scanning technology — including CT scanners now being rolled out at many airports — the 100ml limit remains the default standard in most of the world.

The 3-1-1 Rule (United States)

The United States Transportation Security Administration (TSA) uses what it calls the 3-1-1 rule:

3.4 oz (100ml) or less per container
1 quart-sized (approximately 1 litre) clear, resealable plastic bag
1 bag per passenger

The US rule is numerically identical to the EU rule — 100ml per container, 1-litre bag — though marketed differently. The key practical difference is that American quart-size bags tend to be slightly larger than European versions, giving you marginally more space for containers.

At TSA checkpoints, you must remove your liquids bag from your carry-on and place it separately in a bin for X-ray screening.

The 100ml Rule (EU, UK, and Most Countries)

The European version of the rule, now adopted across the EU, UK, Canada, Australia, Japan, Singapore, and most other countries, works as follows:

Each container must hold no more than 100ml
All containers must fit in a single transparent, resealable plastic bag
The bag must have a capacity of no more than 1 litre — roughly 20 × 20 cm when flat
Each passenger is limited to one such bag
The bag must be presented separately at the security checkpoint

A crucial point: the size of the container matters, not how full it is. A 200ml bottle that is half empty still violates the rule because the container itself exceeds 100ml.

What Counts as a Liquid?

The definition of "liquid" in aviation security is broader than most people expect. Security agencies classify anything that flows, can be spread, or is not a solid as a liquid for screening purposes. This includes:

Obviously liquids:

Water and all beverages
Juice, wine, spirits
Shampoo, conditioner, body wash
Mouthwash

Less obvious — still classified as liquids:

Toothpaste
Moisturiser and face cream
Sunscreen (lotion or spray)
Foundation and BB cream
Mascara and liquid eyeliner
Lip gloss and lip balm (if gel-like)
Hair gel and pomade
Gel deodorant (solid stick deodorant is fine)
Perfume and cologne
Peanut butter and nut butters
Hummus and dips
Yoghurt
Soft cheeses (brie, cream cheese)
Jam and honey

Solid items that are NOT liquids:

Stick deodorant
Solid soap bars
Hard cheese
Powder (dry makeup, dry shampoo)
Solid food (sandwiches, fruit, chocolate)
Tablets and pill medications

When in doubt, apply the "squeeze test": if you can squeeze it out of a container or spread it on something, it's a liquid for security purposes.

Exemptions: What You Can Take in Larger Quantities

Several categories of liquid are exempt from the 100ml rule and do not need to go in your liquids bag:

Medications

Prescription and over-the-counter medications in liquid form are permitted in quantities exceeding 100ml. You should:

Declare them separately at the security checkpoint
Keep them in original packaging where possible
Carry a prescription or doctor's note for prescription medications, particularly for large volumes or unusual substances
Be prepared for additional screening

Baby Milk and Infant Food

Baby formula (powdered or liquid), breast milk, and liquid baby food are all exempt. You can bring the amount reasonably needed for the journey. A parent traveling without an infant is generally not granted this exemption, though policies vary by country.

Duty-Free Liquids

Alcohol, perfumes, and other liquids purchased at airport duty-free shops after security may be brought on board in quantities above 100ml, provided they are:

In the original, sealed, tamper-evident bag from the retailer
Purchased from a Security Tamper-Evident Bag (STEB)-compliant retailer
Accompanied by the purchase receipt inside the bag

Important: On connecting flights, check the rules for your layover country before purchasing. Some countries conduct secondary security checks at transit, and duty-free liquids from certain origins may be confiscated.

Airport Security Process for Liquids

What You Need to Do

Before security: Pack all liquids in your 1-litre transparent bag and keep it accessible in the top of your carry-on or in an outer pocket
At the checkpoint: Remove the liquids bag from your carry-on and place it in a tray for separate X-ray screening
Declare exemptions: Separately declare medications, baby milk, or other exempt items to the officer before the belt
After screening: If your bag is flagged for a swab test or manual inspection, wait calmly — officers may test liquids with an explosives trace detector

What Happens If You Fail

Containers over 100ml are confiscated — there is no option to transfer the contents to a smaller bottle at the checkpoint
Items that are not in the transparent bag may be confiscated or you may be asked to repack before re-screening
In the US, TSA PreCheck members may not need to remove liquids or laptops at TSA lanes — check your eligibility

Practical Tips for Packing Liquids

Use Travel-Sized Containers

Rather than carrying full-size products and transferring them, invest in a set of reusable travel bottles in 30ml, 50ml, and 100ml sizes. Silicone bottles compress when empty and are leak-resistant. Label them clearly.

Go Solid Where Possible

Solid alternatives to common liquids have improved significantly:

Shampoo bars replace liquid shampoo
Solid conditioner bars work like conditioner
Bamboo soap bars replace body wash
Toothpaste tablets replace liquid or gel toothpaste
Solid sunscreen sticks replace SPF lotion

None of these count as liquids, so they can be any size and don't need to go in the bag.

Buy After Security

Water and beverages purchased airside are allowed on the plane. For everything else, consider purchasing at your destination rather than carrying products through security.

Pack a Spare Bag

The 1-litre bag provided at many airports is flimsy and often doesn't seal well. Bring your own resealable freezer bag or a purpose-made liquids bag with a zip closure.

Know Your Airport

Security standards and how strictly they're applied vary significantly by airport. Some airports use CT scanners that can identify liquids without removing them from your bag — check whether your departure airport uses this technology. Even if it does, you may still be asked to remove your liquids if the scanner flags anything for review.

The Bottom Line

The 100ml liquid rule is consistent across most of the world: containers must be 100ml or less, and everything must fit in one 1-litre transparent bag. The US 3-1-1 rule is functionally identical. Medications, baby milk, and sealed duty-free purchases are the main exemptions. The easiest way to avoid problems is to switch to solid alternatives where you can, buy liquids at your destination, and keep your small liquid containers in an organized, accessible bag so the security process stays quick and stress-free.