The TSA liquid rules are simpler than the queue at the checkpoint suggests, and the part that catches people out is almost never the 3.4 ounce limit itself. It is the things that count as a liquid when you would not expect them to, and the exemptions that are never printed on the sign above the bins.
Everything below comes from the Transportation Security Administration’s own published guidance, including the medication and infant rules that let you carry far more than a quart bag holds. Read it once and you can pack a carry-on without ever repacking it on a metal table.
The TSA Liquid Rules in One Sentence
You may bring one quart-sized bag of liquids, aerosols, gels, creams and pastes through the checkpoint, and every container in it must hold 3.4 ounces (100 millilitres) or less. That is the whole rule, and the three numbers give it the name 3-1-1.
- 3.4 ounces: the maximum size of each container, not the amount of product inside it.
- 1 quart-sized bag: one per passenger, and everything liquid has to fit inside it.
- 1 bag per traveller: a family of four may carry four bags, one each.
- Anything bigger goes in the hold, which TSA states directly for containers over 3.4 ounces.
The container size is what matters, not how full it is. A half-empty 8 ounce bottle of shampoo is not allowed through, because the container is over the limit even though the liquid in it is not. This is the single most common reason a bag gets pulled at the belt.
What Counts as a Liquid at the Checkpoint
TSA reads “liquid” broadly, and its own item-by-item guidance puts several solid-looking things in the same category as shampoo. If it can be spread, squeezed, poured or sprayed, assume it is a liquid. Anything in a bottle counts, including the products in our guide to the best personal lubricants.
- Peanut butter: allowed in a carry-on only in containers of 3.4 ounces or less.
- Mascara and liquid foundation: the same 3.4 ounce cap as any other liquid.
- Toothpaste, sunscreen and deodorant creams: pastes and gels, not solids.
- Yoghurt, hummus, jam and soft cheese: food, but liquid as far as screening goes.
- Snow globes: allowed only if the globe appears to hold under 3.4 ounces, roughly tennis ball sized, and the whole thing including the base fits in your quart bag.
Stick deodorant, bar soap and solid perfume are not liquids and do not need to go in the bag at all, which is a useful way to free up space. Powders are a separate category: they are allowed, though quantities over 12 ounces may be pulled for extra screening on flights into the United States.
The Exemptions That Are Not on the Sign
Three groups of liquids are allowed through in quantities well over 3.4 ounces, and they do not have to fit inside the quart bag. Declare them to an officer at the start of screening rather than letting the X-ray find them.
- Medication: permitted in reasonable quantities for your trip, and it does not need to fit in the quart bag.
- Infant and child nourishment: formula, breast milk, toddler drinks and baby food including puree pouches are allowed in quantities over 3.4 ounces.
- Cooling accessories: ice packs, freezer packs and gel packs are allowed whether or not breast milk is present.
- Duty free bought abroad: allowed over 3.4 ounces on a connecting flight into the US if it is sealed in a tamper-evident bag with the receipt, dated within the last 48 hours.
The infant rule is broader than most travellers realise. TSA’s guidance for families states that your child does not have to be travelling with you to carry breast milk and cooling accessories through the checkpoint, and that these items do not need to fit within a quart-sized bag. Liquids in pouches may get alternate screening such as vapour analysis, and nothing is put into the liquid itself.
How Much Liquid a Checked Bag Can Hold
Checked baggage has limits too, which is a surprise to anyone who assumes the hold is unrestricted. TSA’s sunscreen guidance spells out the FAA rule for toiletries and medicinal articles, aerosols included.
- 2 kilograms or 2 litres per person in total, which is about 70 ounces by weight or 68 fluid ounces by volume.
- 0.5 kilograms or 500 millilitres per container, roughly 18 ounces or 17 fluid ounces.
- Aerosols count toward that total, and their caps must be protected against accidental release.
For a normal holiday that ceiling is generous. It starts to matter if you are moving house, packing for a long stay abroad, or carrying professional kit such as hair products or paints, where a single bottle can exceed the per-container limit on its own.
Duty Free Liquids and Connecting Flights
A litre of spirits bought airside in Rome is fine until you land in the United States and have to clear security again for a domestic connection. TSA allows it through, but only on four conditions, and missing any one of them means the bottle is surrendered.
- Bought internationally and travelling to the US on a connecting flight.
- Packed by the retailer in a transparent, secure, tamper-evident bag.
- No signs of tampering when you present the bag for screening.
- The original receipt is with it, and the purchase was made within the last 48 hours.
Even then, the contents still have to be screened and cleared, and anything that alarms or cannot be screened will not be allowed into the cabin. TSA recommends packing duty free liquids in checked baggage anyway, which is the safer plan if your connection is tight or the bottle was expensive. A bottle bought on a return leg with no onward US connection is not covered by this exemption at all.
Packing a Quart Bag That Clears First Time
- Use a real quart bag. A one litre freezer bag is close enough in practice, but a gallon bag is not and officers will say so.
- Decant rather than downsize. Refillable 3 ounce bottles hold enough shampoo for a week and cost less than travel minis.
- Put the bag at the top of your carry-on, so you can lift it out without unpacking.
- Separate medication and baby liquids and tell the officer about them before your bag goes on the belt.
- Leave solids out of the bag entirely, which is usually enough to make everything else fit.
One thing that must not go in the hold is a spare battery. Lithium power banks and loose batteries have to travel in the cabin, so a portable power station or a phone battery pack goes in the same bag as your liquids, not in the suitcase you check. An electric toothbrush carries a lithium cell for the same reason, and our guide to the best electric toothbrushes notes which models ship with a travel case.
If you have TSA PreCheck the quart bag can stay inside your carry-on along with your laptop, which is most of the reason the lane moves faster. Without it, a bag left buried is what turns a 20 second screening into a manual search.
What Happens If You Get It Wrong
Nothing dramatic. An oversized bottle is surrendered at the checkpoint and binned, and you carry on to your gate. The cost is the product and the delay, not a fine, though the delay is the part that matters on a tight connection.
Two points are worth knowing. Anything that alarms during screening gets additional screening whatever its size, so a compliant bottle can still slow you down. And the final decision on any item rests with the officer at the checkpoint, which is why borderline items are better packed in the hold. Cleaning sprays are a good example, and even the gentle ones covered in our guide to cleaning a computer screen belong in a checked bag rather than a carry-on if the bottle is over the limit.
Frequently Asked Questions
How many liquids can you take on a plane?
As many as fit in one quart-sized bag, provided no single container holds more than 3.4 ounces or 100 millilitres. There is no cap on the number of containers beyond what the bag physically holds, and each passenger gets their own bag.
Can you bring a full-size deodorant on a plane?
A solid stick deodorant, yes, in any size, and it does not need to go in the quart bag. A gel, cream or spray deodorant is treated as a liquid, so it has to be 3.4 ounces or less in a carry-on or travel in your checked bag. Makeup splits the same way: a pencil is a solid, while a liquid liner is not, as our guide to the best eyeliner notes.
Do medications count toward the liquid limit?
No. TSA permits medically necessary liquids in reasonable quantities for your trip, and they do not have to fit inside the quart-sized bag. Take them out and tell an officer at the start of screening so they can be screened separately.
Can you bring an empty water bottle through security?
Yes. An empty bottle is not a liquid, and filling it after the checkpoint is the cheapest thing you can do at an airport. Make sure it is genuinely empty, because even a mouthful left in the bottom will have you sent back to a bin.
