Volume Converter

What this calculates

Enter a volume in millilitres, cubic centimetres, litres, cubic metres, US fluid ounces, US cups, US pints, US quarts, US gallons, UK fluid ounces, UK pints, UK gallons, cubic inches or cubic feet, and this shows it in all fourteen at once, with each conversion worked through. It also places the volume on a scale running from a tenth of a millilitre to 10,000 cubic metres, so a fluid ounce and a cubic metre can be read against each other.

US and UK units share names but not sizes, so every one of them is labelled US or UK. Every figure comes from exact definitions — nothing is converted with a rounded shortcut factor.

The formula

Every conversion goes through litres: into litres with one unit's size, then out again with another's.

The metric units are powers of ten: a litre is 1,000 mL, a cubic centimetre is exactly a millilitre, and a cubic metre is 1,000 L. The US units and the cubic foot all build on the cubic inch.

The UK units build on the UK gallon, which is defined directly in litres.

Because every factor is exact, a conversion is exact until it is rounded for display — and the calculator rounds each result once, from the exact figure.

Worked example

Not every conversion comes out round, because a litre is not a whole number of any US or UK unit: each result above is shown to seven significant figures.

Going from a US or UK unit into litres is exact: 1 US gal is 1 × 3.785411784 = 3.785411784 L in the working, and 16 US cups come back as exactly 1 US gal.

When to use it, and the mistakes to avoid

Use it when a label, a set of instructions or a specification gives a volume in a unit you do not think in, when you need to know whether a figure means US or UK gallons, pints or fluid ounces, and when a volume is given in cubic feet or cubic inches and you want it in litres, or the other way round.

The mistakes that cost the most:

• Mixing up US and UK gallons. A UK gallon is 4.54609 L and a US gallon is 3.785411784 L, so 1 UK gal is 1.20095 US gal — about a fifth more. Five UK gallons is 22.73045 L; five US gallons is 18.92706 L. Check which gallon a figure means before converting it.
• Mixing up US and UK pints. The same gap applies: a UK pint is 568.2613 mL and a US pint is 473.1765 mL, so 1 UK pt is 1.20095 US pt. A UK pint is 20 UK fluid ounces; a US pint is 16 US fluid ounces.
• Treating a fluid ounce as a weight. A fluid ounce measures volume. An ounce of weight is a different unit, and how much a fluid ounce weighs depends on what is in it, so this calculator does not convert between them — the weight converter handles ounces of weight. The two fluid ounces also differ: 29.57353 mL for US, 28.41306 mL for UK.
• Using the length factor for a volume. A metre is 3.28084 ft, but a cubic metre is 35.31467 ft³ — the factor is cubed, because a volume is a length times a length times a length. The same goes for inches: 1 ft³ is 1,728 in³, not 12.
• Expecting every digit of every result. Results are shown to seven significant figures — 1 US gal shows as 3.785412 L — while the working keeps the exact litre figure. A volume far too small for a unit, such as 0.000000000001 mL in cubic metres, US gallons, UK gallons or cubic feet, reads as 0, and a note under the result says so rather than leaving a silent zero.
• Entering a negative volume. A volume cannot be less than zero, so the calculator refuses one with a message instead of converting it.

FAQ