US Fluid Ounces to Milliliters converter (fl oz → ml)

fl oz to ml formula

Worked example: 20 fl oz = 591.4706 ml. The defining value behind this factor is documented on our volume & capacity standards page.

US Fluid Ounces to Milliliters chart

Includes standard reference values plus the specific numbers people search for most.

Most-searched fl oz to ml answers

When to convert fl oz to ml

• ▸Cooking & baking — US recipes give fl oz, most of the world uses ml; 9 fl oz of milk is not the same volume as 9 of any other liquid unit.
• ▸Fuel economy — filling 9 fl oz of gasoline in the US vs ml of petrol in Europe helps you compare mpg vs L/100km.
• ▸Nutrition labels — beverage bottles list volume in both fl oz and ml depending on the market.
• ▸Cocktails & bartending — jigger sizes and shot glasses are labelled in fl oz in the US but recipes online often quote ml.
• ▸Lab & chemistry — pipettes, beakers and dosing cups switch between fl oz and ml; conversion matters for accurate reagent volume.

Common mistakes

• ✕Confusing US fluid ounces (29.57 ml) with UK/Imperial fluid ounces (28.41 ml).
• ✕Assuming a "cup" is universal — US = 240 ml, metric = 250 ml, Japanese = 200 ml.
• ✕Weighing liquids instead of measuring by volume when the density is not 1 g/ml.
• ✕A US gallon and a UK gallon are not the same size. US liquid gallon = 3.785411784 L. Imperial (UK) gallon = 4.54609 L. The imperial gallon is about 20.1% larger. Fuel-economy figures in mpg are therefore not comparable between the US and the UK unless the gallon is specified.

Regional usage & source

Liters and milliliters are used worldwide. The US fluid ounce (~29.57 ml) is different from the UK/Imperial fluid ounce (~28.41 ml) — recipes must specify which one. A US cup is 240 ml; a metric cup is 250 ml.

Reference: 1 US liquid gallon = 3.785411784 L; 1 Imperial gallon = 4.54609 L (NIST SP 811).

How these numbers are produced and rounded: methodology.

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