A volume converter changes a capacity from one unit into another — litres to gallons, millilitres to fluid ounces, or cups to pints. It is essential when following recipes written abroad, comparing fuel and drink container sizes, or reading engine and tank capacities. This tool covers metric units (mL, L, m³) alongside both US customary and Imperial units, which matters because a US gallon and an Imperial gallon are not the same size.
The formula. Every value passes through one base unit, the litre. The key factors are 1 mL = 0.001 L, 1 m³ = 1,000 L, 1 US fluid ounce = 0.0295735 L, 1 US cup = 0.2365882 L, 1 US gallon = 3.7854118 L and 1 Imperial gallon = 4.5460900 L. A value is multiplied to litres, then divided by the target unit's factor: result = value × factor(from) ÷ factor(to).
Worked example. A 5 US gallon water jug holds 5 × 3.7854118 = 18.93 litres. The same 5 gallons quoted in Imperial measure would be 5 × 4.54609 = 22.73 litres — nearly four litres more, which is why UK and US fuel-economy figures never compare directly. A 750 mL wine bottle is 0.75 L, or about 25.4 US fluid ounces.
Where it's used. Volume conversion is everywhere in the kitchen and the garage: American recipes use cups and fluid ounces while the rest of the world weighs or measures in millilitres, fuel is sold by the litre in most countries and the gallon in the US, and engine displacement is quoted in litres or cubic centimetres. Note that a US pint is 473 mL while an Imperial pint is 568 mL — a 20% difference hiding behind the same word.