What the volume list actually contains
The converter holds thirteen volumes against the litre: ml, litre, cubic metre, then the US customary teaspoon, tablespoon, fluid ounce, cup, pint, quart and gallon, plus the imperial (UK) fluid ounce, pint and gallon. The teaspoon, tablespoon, cup and quart are US ones. The US system is built from the gallon of 231 cubic inches, which is exactly 3.785411784 L, and divided by halving steps: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces. A cup is 8 US fluid ounces, 236.588 ml, and a tablespoon is 14.787 ml (three teaspoons at 4.929 ml).
US versus imperial gallons
The imperial gallon was defined in 1824 from the volume of ten pounds of water and is now exactly 4.54609 L, about 20% larger than the US gallon (the ratio is 1.201). Imperial pints, quarts and fluid ounces scale with it: an imperial pint is 568.26 ml (20 imperial fl oz) against the US pint of 473.18 ml (16 US fl oz). The list has the imperial pint, fluid ounce and gallon, so a British recipe's pint converts directly. The difference also shows up in fuel economy: a car doing 40 mpg (imperial) does about 33.3 mpg in US gallons.
Worked examples
- 250 ml in cups: 250 / 236.5882365 = 1.057 US cups. Australia and New Zealand use a 250 ml metric cup, so a recipe from there lands slightly differently from the US result.
- 10 L is 2.642 US gallons, but only 2.200 imperial gallons.
- A 44 L fuel tank holds 11.62 US gallons or 9.68 imperial gallons.
- 1 L is 4.227 US cups and 1.057 US quarts.
Cooking pitfalls
- Fluid ounces are volume, not weight. A cup of flour is about 120 g, a cup of water about 237 g, so never turn "8 fl oz" into "8 oz" on a scale. For mass, use the weight converter.
- Tablespoon size varies. The US tablespoon is 14.79 ml here. Australia uses 20 ml for a tablespoon, and several metric countries use 15 ml. The tool does not offer these variants, so type the millilitre amount yourself.
- Powders. The conversion is purely volumetric, so a packed or heaped cup of a powder is not guaranteed to match a measured one.
| US unit | Millilitres | Fluid ounces |
|---|---|---|
| 1 teaspoon | 4.929 | 1/6 |
| 1 tablespoon | 14.787 | 1/2 |
| 1 cup | 236.588 | 8 |
| 1 pint | 473.176 | 16 |
| 1 quart | 946.353 | 32 |
| 1 gallon | 3,785.41 | 128 |
For the history of the two systems see metric vs imperial units.