ml to fl oz Converter

Two fluid ounces, and the counterintuitive part

Here is the part that surprises people who already know about gallons: the Imperial fluid ounce is smaller than the US one, even though the Imperial gallon is larger. The difference is only about 4%, running the opposite way to the 20% gallon gap.

It happens because the two systems divide their gallons differently. An Imperial gallon contains 160 Imperial fluid ounces; a US gallon contains 128 US fluid ounces. A bigger gallon cut into more pieces produces smaller pieces. So knowing the gallon relationship and assuming fluid ounces follow it gives you an answer that is wrong in both magnitude and direction.

Pints are where it becomes visible

A US pint is 16 US fluid ounces, which is 473 ml. An Imperial pint is 20 Imperial fluid ounces, which is 568 ml. That is a 20% difference and it is why a pint of beer in London is noticeably larger than a pint in New York.

The same split runs through cups and quarts. Any recipe using pints without stating its origin is genuinely ambiguous, and the error is large enough to matter in baking. Metric recipes avoid the problem entirely by specifying millilitres, which mean the same thing everywhere.

Drink sizes worth recognising

A standard European soft drink can is 330 ml, which is 11.16 US fl oz. An American can is 12 US fl oz, which is 355 ml. A small wine bottle is 375 ml; a standard bottle is 750 ml, which is 25.36 US fl oz. A US shot is typically 1.5 fl oz or 44 ml, while a UK single is 25 ml or 35 ml depending on the venue.

Airline liquid limits are a practical case: the 100 ml rule is often stated as 3.4 oz, which is the US fluid ounce conversion rounded down. A container labelled 3.5 oz is over the limit even though it looks close.

Fluid ounces are not ounces

Worth restating because it causes constant confusion: a fluid ounce measures volume and an ounce measures mass. They are related only for water, and only approximately — one US fluid ounce of water weighs about 1.043 ounces.

For anything denser or lighter than water the relationship collapses. A fluid ounce of honey weighs about 1.5 ounces; a fluid ounce of oil weighs about 0.96. If a recipe says "8 oz of milk" it almost certainly means fluid ounces, and if it says "8 oz of butter" it almost certainly means weight. The grams to ounces converter covers the mass side.

Frequently asked questions