Fluid ounces are used to measure liquids, but the US and UK do not use exactly the same measurement.
This difference can cause confusion when following recipes, reading product labels or converting bottle sizes.
Although both systems use the term fluid ounce, their definitions are different.
What Is a US Fluid Ounce?
One US fluid ounce equals exactly:
It is part of the US customary measurement system.
What Is a UK Imperial Fluid Ounce?
One UK imperial fluid ounce equals exactly:
It belongs to the British imperial measurement system.
Main Differences
| Measurement | US fluid ounce | UK fluid ounce |
|---|---|---|
| 1 fl oz | 29.57 ml | 28.41 ml |
| 2 fl oz | 59.15 ml | 56.83 ml |
| 4 fl oz | 118.29 ml | 113.65 ml |
| 8 fl oz | 236.59 ml | 227.30 ml |
| 16 fl oz | 473.18 ml | 454.61 ml |
| 32 fl oz | 946.35 ml | 909.93 ml |
Why Does the Difference Matter?
Imagine you are following an American recipe that asks for 8 fluid ounces of milk.
If you use the UK imperial fluid-ounce measurement instead, you will measure a smaller quantity.
This difference can matter when following precise recipes or preparing measured liquids.
How to Convert ML into US Fluid Ounces
Divide the millilitre value by 29.5735296.
How to Convert ML into UK Fluid Ounces
Divide the millilitre value by 28.4130625.
Which Measurement Should You Use?
- Use US fluid ounces for American recipes and US product measurements.
- Use UK imperial fluid ounces when following recipes that explicitly use imperial measurements.
- Use millilitres when you want a consistent metric measurement.
For quick calculations, try our US Fluid Ounces Converter or UK Fluid Ounces Converter.
