Ounces to Millilitres Converter

How to Convert Fluid Ounces to Millilitres

The conversion from fluid ounces to millilitres depends on whether you are using the US fluid ounce or the Imperial (UK) fluid ounce. The two are different units, so it matters which system the recipe or label uses.

• US fluid ounce: 1 fl oz = 29.5735295625 mL (exactly, by definition)
• Imperial fluid ounce: 1 fl oz = 28.4130625 mL (exactly, by definition)

To convert, multiply the number of fluid ounces by the relevant factor:

mL = fl oz x 29.5735 (US)  or  mL = fl oz x 28.4131 (Imperial)

To convert back from millilitres to fluid ounces, divide by the same factor:

fl oz = mL / 29.5735 (US)  or  fl oz = mL / 28.4131 (Imperial)

Worked Example

Default inputs: 8 US fl oz

• mL = 8 x 29.5735295625 = 236.59 mL
• Litres = 236.59 / 1000 = 0.2366 L

This is exactly 1 US cup (which is defined as 8 US fl oz = 236.588 mL). Handy to remember when scaling recipes.

US vs Imperial Fluid Ounces

The US fluid ounce and the Imperial fluid ounce are similar but not identical. The US fluid ounce is approximately 4.1% larger than the Imperial fluid ounce. This small difference matters when precision is important, such as in pharmaceutical dosing or scientific work.

When Does It Matter?

Most printed recipes from the United States and international product labels use US fluid ounces. UK and older Commonwealth recipes may use Imperial fluid ounces. In New Zealand, volumes are typically given in millilitres or litres, so this converter is useful when following recipes from American websites or measuring liquid ingredients in US-labelled measuring tools.

Quick Reference: Fluid Ounces in Millilitres

• 1 fl oz (US) = 29.57 mL
• 2 fl oz (US) = 59.15 mL
• 4 fl oz (US) = 118.29 mL (half a US cup)
• 8 fl oz (US) = 236.59 mL (1 US cup)
• 12 fl oz (US) = 354.88 mL (standard can of drink)
• 16 fl oz (US) = 473.18 mL (US pint)
• 32 fl oz (US) = 946.35 mL (US quart)
• 128 fl oz (US) = 3,785.41 mL (US gallon)

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Sources: National Institute of Standards and Technology (NIST) Handbook 44, Appendix C: General Tables of Units of Measurement. International Bureau of Weights and Measures (BIPM): The International System of Units (SI).

This converter uses the exact defined values for US and Imperial fluid ounces. For cooking purposes, rounding to 1 or 2 decimal places is sufficient. For pharmaceutical or scientific use, apply the full precision factors given above.