How to use the volume converter
- Type the amount in Value.
- Choose its unit in From. Units are labelled “US” or “UK”, so pick the one that matches the source of your figure.
- Choose the unit you want in To; the converted amount appears immediately.
- Look at the table for the amount in every unit, including millilitres, cubic inches and oil barrels.
- Swap the units with the button if you need the reverse conversion.
What it does and when to use it
The converter covers 18 units: cubic metres, litres, millilitres and cubic centimetres; US gallons, quarts, pints, cups, fluid ounces, tablespoons and teaspoons; UK gallons, quarts, pints and fluid ounces; cubic feet and cubic inches; and the 42-gallon oil barrel.
Use it for fuel and car economy figures from another country, for the size of a fish tank or water tank, for recipes written in US cups, for a drink served in pints, or for shipping and storage space in cubic feet. When an amount is given as a flat area and a depth, such as a garden bed or a concrete slab, find the area with the area converter, multiply by the depth in the same unit, and then convert the result here.
How it works
Every unit is stored as a number of litres:
- US gallon = 231 cubic inches = 3.785411784 L. The quart, pint, cup, fluid ounce, tablespoon and teaspoon are 1/4, 1/8, 1/16, 1/128, 1/256 and 1/768 of it.
- UK gallon = 4.54609 L, as set by the UK Weights and Measures Act 1985. The UK quart, pint and fluid ounce are 1/4, 1/8 and 1/160 of it.
- Cubic foot and cubic inch come from the exact inch of 2.54 cm, cubed.
Your value is multiplied by its size in litres and divided by the size of the target unit.
A detail that surprises people: the UK gallon is bigger, but the UK fluid ounce (about 28.41 mL) is smaller than the US one (about 29.57 mL). That is because the UK divides its gallon into 160 fluid ounces and the US divides its smaller gallon into 128.
Worked examples
All three come straight from the converter.
Filling up in the US. 1 US gallon = 3.785411784 litres. Ten gallons of fuel is about 37.9 litres.
UK against US gallons. 1 UK gallon = 1.2009499255 US gallons, which is why miles-per-gallon figures from the UK look higher than US figures for the same car.
A US recipe cup. 1 US cup = 236.5882365 millilitres. Rounding to 240 mL is close enough for most cooking.
Limits and tips
- Cubic units grow fast. Volume factors are length factors cubed: a metre is 3.28 feet, but a cubic metre is about 35.3 cubic feet. Mixing these up gives errors of thirty times or more.
- Dry measures such as the US dry pint and bushel are not included.
- Baking by volume is imprecise. A cup of flour can weigh quite different amounts depending on how it is filled, so weigh it if the recipe gives grams, and use the weight converter for ounces and pounds.
- For fuel economy in mpg or L/100 km, use the fuel converter, which handles the reciprocal maths correctly.
Frequently asked questions
How many litres are in a gallon?
How many millilitres are in a cup?
Is a pint of beer in London bigger than in New York?
Can I convert fluid ounces to ounces?
How many litres are in a cubic metre?
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