Volume Converter

Convert volume units including liters, milliliters, gallons, cups, cubic meters, and cubic feet.

Volume Converter

Convert between metric and US customary volume units, including millilitres, litres, cubic metres, fluid ounces, cups, pints, quarts, gallons, and cubic feet. Volume is one of the easiest places to pick the wrong unit, because US and imperial measures share names but not sizes.

Conversion factors

The US gallon is defined as exactly 231 cubic inches, and the imperial gallon as exactly 4.54609 litres, so these factors are exact:

  • 1 US gallon = 3.785411784 L (4 quarts, 8 pints, 128 US fl oz)
  • 1 imperial gallon = 4.54609 L (about 20% larger than the US gallon)
  • 1 US fluid ounce = 29.5735295625 mL
  • 1 US cup = 8 US fl oz = 236.5882365 mL (nutrition labels use a rounded 240 mL cup)
  • 1 US quart = 0.946352946 L
  • 1 cubic foot = 28.316846592 L
  • 1 cubic metre = 1,000 L, 1 L = 1,000 mL

Worked example

Convert a 12 US gallon fuel tank to litres:

  • 12 × 3.785411784 = 45.4249..., so the tank holds about 45.42 L.

For cooking, 2 US cups of stock in millilitres is 2 × 236.588 = 473.18 mL, so just under half a litre; using the 240 mL rounded cup gives 480 mL, and either is fine for most recipes.

When to use this converter

  • Cooking and baking: US recipes measure liquids in cups and fluid ounces, while metric recipes use millilitres; converting keeps liquid ratios correct.
  • Travel and fuel: fuel is sold by the litre in most countries and by the gallon in the US, which matters when comparing prices or tank sizes.
  • Shipping and storage: freight volumes, aquarium capacities, and container sizes are quoted in cubic metres, litres, or cubic feet depending on the industry.
  • Home projects: paint, concrete, and soil are sold in litres, gallons, or cubic feet/yards depending on the region and product.

Tips for accurate conversions

  • US and imperial units differ even when the names match. An imperial pint is 568.26125 mL, while a US liquid pint is about 473.18 mL, and an imperial fluid ounce (28.4130625 mL) is slightly smaller than a US fluid ounce.
  • A "cup" is not universal: the US customary cup is about 236.6 mL, US nutrition labelling uses 240 mL, and older Commonwealth recipes may assume a 250 mL metric cup.
  • Fluid ounces measure volume; ounces measure weight. Converting between them requires the density of the substance, which is why 8 fl oz of honey weighs far more than 8 fl oz of flour.
  • US dry measures (dry pints, dry quarts, bushels) are larger than their liquid counterparts and are not covered by the liquid factors above.
  • For fuel economy specifically, converting gallons and litres is only half the job; miles per gallon and litres per 100 km are inverse-style measures with their own conversion.

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Frequently asked questions

How many litres are in a US gallon?
A US gallon is exactly 3.785411784 litres, defined as 231 cubic inches. It contains 4 quarts, 8 pints, or 128 US fluid ounces.
What is the difference between a US gallon and an imperial gallon?
The imperial gallon, still used in the UK and some Commonwealth countries, is exactly 4.54609 L, about 20% larger than the 3.785 L US gallon. This is why UK miles-per-gallon figures look better than US ones for the same car.
How many millilitres are in a cup?
The US customary cup is 8 US fluid ounces, or about 236.6 mL; US nutrition labels round it to 240 mL, and many metric-country recipes use a 250 mL cup. For most cooking the difference is negligible, but in baking it can matter, so check which cup a recipe assumes.
How do I convert cubic feet to litres?
Multiply by 28.316846592, which is exact because a foot is exactly 0.3048 m. For example, a 5 cubic foot refrigerator compartment holds about 141.6 L.
Can I convert fluid ounces to ounces by weight?
Not directly, because fluid ounces measure volume while ounces measure mass. The conversion depends on density: 8 US fl oz of water weighs about 8.35 oz, but the same volume of oil, honey, or flour weighs a different amount.
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