Volume converter
Convert between millilitres, litres, cubic metres, fluid ounces, cups, pints and gallons. Why the US and imperial gallons differ by 20%.
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Every volume unit, one page
Pick any two units above. The conversions people look up most often have dedicated pages with reference tables, linked below.
The factors are exact
| Unit | Litres | Note |
|---|---|---|
| Millilitre | 0.001 | one cubic centimetre |
| Litre | 1 | |
| Cubic metre | 1000 | |
| US fluid ounce | 0.0295735295625 | |
| US cup | 0.2365882365 | 8 US fluid ounces |
| US pint | 0.473176473 | 16 US fluid ounces |
| US gallon | 3.785411784 | 231 cubic inches, exactly |
| Imperial gallon | 4.54609 | exact by definition |
There are two gallons and they differ by 20%
This is the largest trap in the whole catalogue of unit conversions. The two gallons are not close:
| Litres | Where | |
|---|---|---|
| US gallon | 3.785 | United States |
| Imperial gallon | 4.546 | United Kingdom, Canada, Caribbean |
A car doing “30 miles per gallon” in the UK is doing about 25 US mpg. Fuel economy figures quoted in mpg are meaningless without knowing which gallon, which is why the metric world uses litres per 100 km instead — a measure that is not a rate of the same kind and cannot be silently misread.
The pints and fluid ounces underneath them differ too:
| US | Imperial | |
|---|---|---|
| Fluid ounces per gallon | 128 | 160 |
| Pint | 473.2 ml | 568.3 ml |
| Fluid ounce | 29.57 ml | 28.41 ml |
Note the reversal: an imperial pint is bigger than a US pint, but an imperial fluid ounce is smaller than a US one. The imperial pint holds 20 ounces where the US pint holds 16. This converter uses US fluid ounces, pints and cups.
A fluid ounce is not an ounce
A fluid ounce measures volume; an ounce measures weight. They are not interchangeable and the relationship between them depends on what the liquid is. Water is the coincidence that makes people think otherwise: one US fluid ounce of water weighs about 1.04 ounces, close enough to look like a rule. Honey, oil and syrup are nowhere near.
For weight, see the weight converter.
Cups are not standardised
If a recipe says “one cup”, it depends entirely on where the recipe is from:
| Cup | Millilitres |
|---|---|
| US customary | 236.6 |
| US “legal” (nutrition labelling) | 240 |
| Metric (Australia, NZ, UK) | 250 |
| Japan | 200 |
| Rice cooker cup (Japan, Taiwan) | 180 |
The rice cooker cup is the one that surprises people: the plastic cup supplied with a rice cooker is 180 ml — one gō, a traditional Japanese unit — and the water lines inside the bowl are calibrated to it. Measuring rice with a 250 ml cup and filling to the line gives the wrong ratio.
This converter uses the US customary cup of 236.6 ml.
Where people go wrong
Millilitres and cubic centimetres are the same thing. 5 ml is 5 cc. Medical and automotive contexts prefer cc; everything else prefers ml.
A cubic metre is a thousand litres, not a hundred. And a cubic decimetre is exactly one litre, which is where the litre came from in the first place.