Liters to Gallons Calculator

Background.

Ask how many gallons are in 55 liters and there are two correct answers: 14.5295 US gallons or 12.0983 imperial gallons. They differ by almost two and a half gallons because the gallon still used in the United States and the one still used in British fuel-economy figures are different units, the imperial one about 20% larger.

Both are now defined exactly in terms of metric units. The US liquid gallon is 231 cubic inches, and since the 1959 international agreement fixed the inch at exactly 2.54 cm, that makes it 3.785411784 liters with nothing left over; NIST Special Publication 811 lists it that way. The imperial gallon is set at exactly 4.54609 liters by the UK Weights and Measures Act 1985. Converting is therefore a single division, and both results are shown side by side whichever gallon you pick.

The usual trap is not the arithmetic but knowing which gallon a source means. A US car manual, a US-made pump or a drum labelled in America uses US gallons. A British mpg figure, or a Canadian or Australian document from before those countries went metric, means imperial gallons.

What is liters to gallons calculator?

A liter is one cubic decimeter, 1,000 cubic centimeters. The US liquid gallon is 231 cubic inches, descended from the old English wine gallon, and is the gallon used for fuel, milk and other liquids in the United States. The imperial gallon, introduced in Britain in 1824 as the volume of ten pounds of water under stated conditions, is now fixed at 4.54609 liters, or about 277.42 cubic inches. One imperial gallon equals 1.2009 US gallons.

How to use this calculator.

1. 01Enter the volume in liters, from a fuel-tank specification, a container label or a meter reading.
2. 02Pick the gallon you need: US for anything American, imperial for British mpg figures and older Commonwealth paperwork.
3. 03Read the converted volume, and glance at the other gallon shown beside it if you are not certain which one your source used.

The formula.

Gallons = liters ÷ f, where f is the size of one gallon in liters: exactly 3.785411784 for the US gallon and exactly 4.54609 for the imperial gallon. The US figure comes from 231 in³ × (2.54 cm/in)³ = 231 × 16.387064 cm³ = 3,785.411784 cm³. The imperial figure is a legal definition and needs no derivation.

Because volumes have no offset — zero liters is zero gallons — the conversion is a pure ratio, and doubling the liters doubles the gallons. For mental arithmetic, multiplying by 0.2642 gives US gallons and multiplying by 0.22 gives imperial gallons; those reciprocals are rounded, whereas dividing by the defined factors is exact.

A worked example.

Frequently asked questions.

References& sources.

1. [1]National Institute of Standards and Technology. NIST Special Publication 811, 2008 Edition - Guide for the Use of the International System of Units (SI), Appendix B. Source for the exact US gallon = 3.785411784 L conversion factor.
2. [2]United Kingdom. Weights and Measures Act 1985, Schedule 1. Statutory definition of the imperial gallon as exactly 4.54609 liters.