How this calculator works
A US fluid ounce is one 128th of a US liquid gallon. The gallon is exactly 231 cubic inches, or 3.785411784 litres, so one fluid ounce is exactly 29.5735295625 millilitres. The conversion is a single multiplication or division by that exact factor. Fluid ounces measure volume; the ounce on a kitchen scale is the avoirdupois mass ounce, which is about 28.35 grams and is not interchangeable with a fluid ounce. The table also shows the same volumes in US customary cups and litres, using 8 fluid ounces per cup and 1000 mL per litre.
Formula
mL = US fl oz x 29.5735295625. US fl oz = mL / 29.5735295625. One US customary cup is 8 US fl oz, so 1 cup = 236.5882365 mL.
Worked example
12 US fl oz is 12 x 29.5735295625 = 354.88235475 mL, which is the value rounded to 355 mL on many drink labels. In reverse, 500 mL is 500 / 29.5735295625 = 16.9070113509 US fl oz.
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Frequently asked questions
Is a fluid ounce the same as an ounce of weight?
No. A fluid ounce measures volume and an avoirdupois ounce measures mass. One fluid ounce of water weighs about 1.043 ounces, and the two numbers diverge for any material with a different density.
Why does a can show 355 mL for 12 fl oz?
Twelve US fluid ounces is 354.88235475 mL. Metric labels round that to 355 mL, so the metric figure is a rounded restatement rather than a second measurement.
Are US and imperial fluid ounces the same?
No. An imperial fluid ounce is 28.4130625 mL, so it is about four percent smaller than a US fluid ounce. Check which ounce a label or recipe uses.