How many liters are there in a gallon?

3.785411784.

The United States Code defines the U.S. liquid gallon to be 231 cubic inches, which is exactly 3.785411784 liters.  The U.S. liquid gallon is most commonly used to denoted the gallon, although other definitions for a gallon exist. There is the less-used U.S. dry gallon and the UK imperial gallon (around 4.5 L) used in the England, Ireland and Canada.