How to Use the Gallon to Liter Converter
Fuel volume units differ by country. Most of the world uses liters (L), but the US uses the US gallon, while the UK and some Commonwealth countries use the UK (imperial) gallon. Despite sharing the name "gallon," the two represent different volumes, which makes them easy to mix up. One US gallon equals 3.78541 liters, while one UK gallon equals 4.54609 liters - about 20% larger than the US gallon.
This gap exists because the two systems were standardized separately. The US gallon derives from the old English wine gallon, while the UK gallon was defined by the 1824 Imperial Weights and Measures Act. As a result, the same "gallon" of fuel pumped in the US versus the UK converts to different liter amounts.
Enter a value, choose a unit, and liters, US gallons, and UK gallons are all calculated at once. Useful when refueling a rental car abroad, checking a fuel tank capacity listed in a US or UK vehicle manual, or reading specs for an imported car.
Frequently Asked Questions
A US gallon is 3.78541 liters, while a UK (imperial) gallon is 4.54609 liters - about 20% larger. The two systems were standardized separately: the US and Canada use the US gallon, while the UK and some Commonwealth countries use the UK gallon.
This calculator only converts fuel volume units. To compare mpg (miles per gallon) figures, you'll also need to convert miles to km along with the gallon-to-liter conversion. US mpg and UK mpg use different gallon sizes, so the same mpg number represents different real-world fuel economy.