The basic liquid measurement unit in the metric system. In most industrial nations outside the United States, motor fuel is now sold by the liter, not by the gallon.

A liter (also spelled litre) is 0.2642 of a U.S. gallon.

In the early 1980s, the Office of Weights and Measures of the U.S. Bureau of Standards coordinated an effort to convert petroleum marketing measurement, in the United States, from gallon units to liter units. Hundreds of  American gasoline stations began selling gasoline by the liter. The public, however, did not perceive advantages in the change, and the effort failed.