Fluid ounces to millilitres converter
The US and imperial fluid ounces differ: pick yours.
Your inputs
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Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
With the millilitres worked out, cups are the natural next jump.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Type the amount in fluid ounces.
- Choose the standard: US or British imperial.
- The result gives millilitres, litres and cups.
- It also shows what it would be under the other standard.
How it is calculated
There are two different fluid ounces and they differ by about 4 %:
The US fluid ounce is defined as 1/128 of a US gallon; the imperial one as 1/160 of an imperial gallon. That the imperial ounce is smaller while the imperial gallon is larger is one of those things only history explains.
Useful trivia: a US pint is 16 fluid ounces and an imperial pint is 20. That is why a British pint of beer is visibly bigger than an American one.
Worked example
A British recipe calls for 10 fl oz of cream:
- Imperial: 10 x 28.413 = 284 ml
- Read as US: 10 x 29.574 = 296 ml
- Difference: 12 ml, just under a tablespoon
Good to know
- British or American. UK recipe, imperial ounce. US recipe, US ounce.
- Not the ounce of weight. The fluid ounce measures volume; the other measures mass. They only roughly coincide for water.
- Different pints. 16 fl oz in a US pint, 20 in an imperial one.
Frequently asked questions
How many ml in a fluid ounce?
29.57 ml for the US fluid ounce and 28.41 ml for the British imperial one, a difference of just over 4 %.
How many ml is 8 fluid ounces?
236.6 ml in the US system, which is exactly one US cup, and 227.3 ml imperial.
Which fluid ounce does my recipe use?
British recipes use the imperial one, American recipes the US one. Modern UK recipes usually give millilitres as well.
Is it the same as an ounce of weight?
No. They share a name and nothing else: one measures volume, the other mass. Only for water do they give similar, and not equal, numbers.