The 3-1-1 liquids rule: how to pack toiletries in a carry-on

A full-size shampoo pulled out at the security queue, a quick decant into something smaller, a cap not quite tight: that is how a bottle ends up leaking into the only clean shirt. Most of it is avoidable, because the rule for liquids in a carry-on is short.

The rule in one line

The US Transportation Security Administration (TSA) calls it the 3-1-1 rule, and its own travel checklist spells out the numbers:

• 3: 3.4 ounces (100 millilitres) or less per container
• 1: one quart-size, clear, plastic, zip-top bag, and all your liquids must fit in it
• 1: one bag per passenger

Anything in a container larger than 3.4 ounces goes in your checked bag. Any liquid, aerosol, gel, cream or paste that alarms during screening will need additional screening.

The limit is on the container, not on what is left in it. The TSA's wording is travel-sized containers of 3.4 ounces or less, and the UK government's guidance says it plainly: the limit still applies if the container is only part full. A half-empty 200 ml bottle of sunscreen is still a 200 ml container, so under the TSA's rule it goes in the checked bag.

What counts as a liquid

The TSA's list is liquids, aerosols, gels, creams and pastes. That covers more than the word liquid suggests. The UK government's guidance names some that are easy to miss: toothpaste, mascara, lip gloss, spray deodorant, hair gel and contact lens solution. The TSA's travel tips page puts it this way: if you can spill it, spread it, spray it, pump it or pour it, and it is larger than 3.4 ounces, it goes in a checked bag.

You will also see bottles sold as "TSA-approved". The rule is about the size of the container, not the brand, so what matters is the capacity on the bottle.

The exceptions

Medicine

The TSA allows liquid medication over 3.4 ounces in carry-on bags in reasonable quantities for the flight. It does not need to go in the zip-top bag, but you must tell the officer about it at the start of screening, and you may be asked to open the containers. Keep it separate from your 3-1-1 bag so it is easy to hand over.

Baby food and milk

Formula, breast milk, toddler drinks and baby or toddler food can go in your carry-on in amounts over 3.4 ounces (100 ml), and they do not need to fit in the quart-size bag. Tell the officer at the start of screening if you are carrying more than 3.4 ounces, and expect them to be screened separately. The TSA's liquids page links to these details on its Traveling with Children page.

Duty free

If you buy duty-free liquids abroad and connect to another flight in the US, you can carry containers over 3.4 ounces only if the shop sealed them in a transparent, tamper-evident bag, the receipt is with them, and you bought them within the last 48 hours. They still have to clear screening. The TSA's own advice is to put liquids over 3.4 ounces in your checked bag anyway, even when they are in a sealed bag.

Packing the bag

Start with the bag itself. The TSA asks for clear and quart-size, and our Clear PVC Quart-Size Toiletry Bag with Zip is sold as a quart-size bag: clear waterproof PVC with a zip, white or black trim, and it wipes clean with mild soap and water. The listing gives no measurements, so when it arrives, check that all your liquids fit inside with the zip closed, as the TSA's checklist requires.

Then the bottles. It pays to use ones made for the job rather than whatever is in the cupboard:

• The Refillable Travel Toiletry Bottles, Set of 5 come as five bottles of one size, in 30, 50 or 100 ml. The listing describes them as flexible squeeze pouches in food-grade plastic with leak-resistant caps. The 30 and 50 ml sizes take up less room in the bag, which leaves space for the things that cannot be decanted. Pick the size by how much of each product you use on the trip.
• The Squeezable BPA-Free Travel Bottles, Set of 4 are refillable squeeze bottles in BPA-free plastic. Their listing does not state the bottle volume yet, and the photos show opaque coloured bottles, so do not count on seeing what is inside. If you are flying through a checkpoint with a 100 ml limit, the set of five, with its sizes stated, is the safer choice for now.

The care notes on both listings agree on hand washing, drying the bottles before refilling and keeping hot liquids and high heat away from them; the set of five also says to wash them thoroughly before first use. Fill them short of the brim so the cap seals cleanly, and pack the bottles upright if the bag allows it.

Put the clear bag where you can reach it without unpacking. The TSA's checklist suggests the front pocket of your carry-on, and in the standard screening lane you take the bag out and put it in the tray.

Everything that is not a liquid

A toothbrush, a comb, a cartridge razor and a spare contact lens case do not need to go through security in the clear bag, and they take up room it does not have. Give them a bag of their own. The Water-Resistant Nylon Cosmetic Bag is 23 × 18 × 10 cm and wipes clean with a damp cloth, which suits the things that get damp in a hotel bathroom. On razors, the TSA's checklist allows shaving blades sealed in a cartridge the blade cannot be removed from, and asks you to keep other razors out of the carry-on.

If you are checking a bag as well, the full-size bottles can travel there, and the hanging kit can too. The Foldable Hanging Toiletry Organizer in Oxford Fabric has a hook to hang it up in a hotel bathroom and separate compartments for small things, and it folds compactly for the case. It is wipe-clean only, not machine washable.

Two bags, then: a clear one that goes through security, and one for everything else.

Outside the US

The TSA's rule covers US airports. Other countries set their own, and they are not always the same. In the UK, the rules depend on the airport. The UK government's guidance says most airports still limit containers to 100 ml, some allow containers of up to 2 litres, and where a bag is required it must be a single transparent, resealable bag holding no more than a litre, about 20 × 20 cm, one per person.

Check the rules at the airport you fly from and at every airport you pass through, including on the way home. A connecting airport can have a different rule from the one you started at.

Before you leave for the airport

• Every liquid, gel, cream, paste and spray is in a container of 100 ml or less
• They all fit in one clear bag, and it zips shut
• Liquid medicines are packed separately, ready to declare
• Anything larger is in the checked bag, or left at home
• The clear bag is in an outside pocket, not at the bottom of the case
• You have checked the liquid rules for every airport on the route