Fluid ounce
A fluid ounce measures volume, not weight. A US fl oz is 29.6 ml and a British one is 28.4 ml. Here is how they compare to cups and pints.
Also called fl oz, Fluid ounces, Imperial fluid ounce.
A fluid ounce (fl oz) is a unit of volume used for liquids in American and older British recipes. It is not the same as an ounce, which measures weight. There are two versions. The US fluid ounce is 29.57 ml. The British, or imperial, fluid ounce is 28.41 ml.
Why it works
A fluid ounce of water weighs almost exactly an ounce, which is where the name comes from. That match only works for water and liquids close to it, such as milk or stock. A fluid ounce of honey weighs about 1.5 ounces, and a fluid ounce of oil weighs a little less than an ounce.
How to use it
The difference between the two fluid ounces is small, but the cups and pints built from them are not the same size, because a US pint holds 16 fluid ounces and an imperial pint holds 20.
| Measure | US | Imperial (UK) |
|---|---|---|
| 1 fl oz | 29.6 ml | 28.4 ml |
| 2 tablespoons | about 1 fl oz | about 1 fl oz |
| 1 cup | 8 fl oz, 237 ml | not a standard unit |
| 1 pint | 16 fl oz, 473 ml | 20 fl oz, 568 ml |
| 1 quart | 32 fl oz, 946 ml | 40 fl oz, 1.14 liters |
For quick work, 1 fl oz is about 30 ml.
Liquid measuring jugs in the US and UK often have fluid ounces on one side and milliliters on the other. Read them at eye level on a flat surface.
Common mistakes
- Weighing 8 ounces of flour when the recipe says 8 fluid ounces. Those are very different amounts.
- Using a British pint for an American recipe, or the other way round. The British pint is 20 percent larger.
- Reading "oz" on a can label as volume. Can labels give net weight in ounces, except for some drinks, which say "fl oz".
In recipes
You will see "8 fl oz (240 ml) milk", "a 12 fl oz bottle of beer" and "½ pint (10 fl oz) double cream" in British recipes. A shot of spirits in the US is usually 1.5 fl oz, about 44 ml.
Related terms
- OunceAn ounce (oz) is a unit of weight, about 28 g. It is not the same as a fluid ounce, which measures volume. Here is how to convert ounces to grams.
- CupA US cup is about 240 ml, a metric cup is 250 ml, and a cup of flour weighs far less than a cup of sugar. Here is how to measure and convert.
- PintA US pint is 473 ml and a British pint is 568 ml, a fifth larger. Here is how to tell which one a recipe means and how to convert it.
- QuartA US quart is 946 ml, just under a liter, and equals 4 cups or 2 pints. The old British quart is larger. Here is how to convert quarts.
- MilliliterA milliliter (ml) is a thousandth of a liter, the metric unit for measuring liquids. See how ml converts to teaspoons, cups and fluid ounces.
- TablespoonA tablespoon is about 15 ml in the US, UK and Sweden but 20 ml in Australia. It equals 3 teaspoons. Here is how to measure and convert it.