Everyone else built a calculator that restates the 100 ml rule. This one solves the actual problem: what fits in the quart bag, what to swap, and what has to be checked.
Not a restatement of the rule. List what you actually own and this solves the packing: what fits the quart bag, what to swap for travel sizes, and what has to be checked.
The limit is 100 ml (3.4 fl oz) per container, and every container must fit inside one transparent resealable bag of about one quart. The container size counts, not how full it is.
Liquids, gels, creams, pastes and aerosols travel through security in containers of 100 ml (3.4 fl oz) or less. Every container must fit inside one transparent resealable bag of roughly one quart, and you get one such bag per passenger.
The number that matters is printed on the container, not the amount left inside it. A half-empty 200 ml bottle of shampoo is a 200 ml container and will be taken off you.
A quart is 946 ml, but you will never fit 946 ml of bottles into a quart bag. Bottles are rigid, they do not tessellate, and the bag has to close. Planning to about 80 per cent of the nominal volume is what actually works in practice, which is why this tool does that rather than flattering you with a number you cannot achieve.
Medication, baby formula, breast milk and juice for an infant are exempt from the 100 ml limit in reasonable quantities. They do not go in the quart bag and they should be declared at the checkpoint, where they may be screened separately. Duty-free liquids bought airside travel in a sealed tamper-evident bag with the receipt inside — but if you have a connection, check whether the transfer airport will accept it, because many will not.