Volume Converter

Metric, US and imperial volume

Metric volume is length cubed. A cubic meter is a cube 1 m on each side and holds 1,000 liters. Since 1964 the liter has been exactly one cubic decimeter, so a milliliter is exactly one cubic centimeter. (From 1901 to 1964 the liter was the volume of a kilogram of water, about 1.000028 dm³, a difference that only matters in old laboratory data.)

US liquid measure is built on a gallon of exactly 231 cubic inches, which the 1959 inch makes 3.785411784 L. Everything below it is a fixed fraction:

• 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces
• 1 fluid ounce = 2 tablespoons; 1 tablespoon = 3 teaspoons

British imperial measure uses a larger gallon, originally the volume of 10 pounds of water and now fixed at exactly 4.54609 L. The imperial pint is ⅛ of it and the imperial fluid ounce 1/160, so an imperial pint holds 20 fluid ounces where a US pint holds 16.

The conversion formula

Every unit has an exact size in liters, and converting multiplies by the ratio of the two sizes:

value

the volume you enter

size

one unit in liters, e.g. 3.785411784 L for a US gallon and 0.001 L for a milliliter

Cubic units follow from lengths: a cubic inch is 2.54 × 2.54 × 2.54 = 16.387064 cm³ exactly, and a cubic foot is 0.3048³ m³ = 28.316846592 L. When the factor in one direction would be a never-ending decimal, the calculator divides by the exact factor for the other direction instead, so the working always shows defined numbers.

Worked examples

A 500 mL bottle in fluid ounces. One US fluid ounce is 29.5735295625 mL, so 500 ÷ 29.5735295625 = 16.90701135 US fl oz. That is why half-liter water bottles sold in the US are labeled 16.9 fl oz.

2 US cups in milliliters. A customary cup is 1/16 of a US gallon: 2 × 236.5882365 = 473.176473 mL, exactly one US pint. A cook using a 250 mL metric cup would measure 500 mL, about 6% more.

A British pint in US pints. 568.26125 mL ÷ 473.176473 mL = 1.200949926, so an imperial pint is about 20% larger than a US pint.

Common volume conversions

All US and imperial figures in metric are exact; the last two rows are rounded.

US versus imperial, and other traps

• Same name, different size. An imperial gallon is 1.200949926 US gallons, and an imperial pint is about 20% larger than a US pint. The imperial fluid ounce, on the other hand, is about 4% smaller than the US one (0.9607599404 US fl oz). Fuel economy follows the gallon: 40 miles per imperial gallon is about 33.3 miles per US gallon.
• Three different cups. This converter’s US cup is the customary cup of 8 US fluid ounces, 236.5882365 mL, which is what American measuring cups hold. US nutrition labels use a rounded legal cup of 240 mL (with 15 mL tablespoons, 5 mL teaspoons and 30 mL fluid ounces), about 1.4% more. Many other countries use a 250 mL metric cup, about 5.7% more.
• Spoons vary too. A US tablespoon is 14.78676478125 mL; Australia uses a 20 mL tablespoon. For baking, check which one a recipe was written with.
• Dry measures are separate. The US also has dry pints, quarts and bushels for produce, which are larger than the liquid units of the same name (a dry pint is about 551 mL). This converter uses liquid measure only.
• Fluid ounces are volume, ounces are weight. A cup of flour and a cup of water fill the same volume but weigh very different amounts. Converting between them needs the ingredient’s density; the weight converter handles the ounces that measure mass.