Most people know there is a rule about liquids. Fewer people know exactly what it says, which is why security bins fill up with confiscated shampoo every day. Here is the actual rule, in plain English.

The 3-1-1 rule

The TSA limit for liquids in carry-on baggage is built on three numbers:

  • 3.4 — each container must hold no more than 3.4 fl oz (100 ml).
  • 1 — all those containers must fit in one quart-sized, clear, resealable bag.
  • 1 — one such bag per passenger.

The size printed on the container is what matters, not how much is left inside it. A half-empty 8 oz bottle is still an 8 oz container, and it will still be taken off you.

What counts as a liquid

More than you would think. The TSA treats anything pourable, spreadable, sprayable, or squeezable as a liquid, which includes:

  • Shampoo, conditioner, body wash, and body lotion
  • Toothpaste and any gel
  • Liquid foundation, mascara, and lip gloss
  • Aerosols and spray deodorant
  • Peanut butter, yoghurt, and honey — genuinely

Solid items are not liquids. Bar soap, solid deodorant, shampoo bars, powder, and a toothbrush all travel freely outside the bag.

The exceptions

A few things are allowed in larger quantities, but you must declare them at the checkpoint and expect additional screening:

  • Medication, liquid or gel, in reasonable quantities for your trip
  • Baby formula, breast milk, and baby food, if you are travelling with a child
  • Duty-free liquids bought after security, if they are sealed in a tamper-evident bag with the receipt inside

The real constraint is the bag, not the bottle

Here is the part people miss. The 3.4 oz limit is rarely what catches you out — the quart bag is. A quart bag holds roughly six to eight travel bottles if you pack it well. Shampoo, conditioner, body wash, lotion, toothpaste, and a face product will fill it before you have packed anything else.

Which means the useful question is not how small are my bottles but how few bottles can I get away with. Every bottle you remove buys space for something else.

That is the thinking behind our travel-size range. Each bottle is 3.3 fl oz — inside the limit — but holds two products rather than one, with a flip-top cap on each side. A shampoo and conditioner take one slot in the bag instead of two.

A quick pre-flight check

  1. Every container 3.4 oz or smaller? Check the label, not the contents.
  2. Everything inside one quart bag that actually closes?
  3. Bag somewhere you can reach without unpacking the whole case?
  4. Medication and baby items separate and ready to declare?

Do that and you will walk through. For more on our bottles and sizes, see the FAQs.

Rules can change and are enforced at the discretion of the officer at the checkpoint. Check the TSA website before you fly if you are carrying anything unusual.