The liter (L) is the most widely used metric unit of volume, equal to 1,000 cubic centimeters or one cubic decimeter, serving as the standard for beverages, fuel, and household liquids worldwide. Gasoline prices, bottled water, and milk cartons all reference liters in most countries. One liter equals approximately 1.0567 US quarts or 0.2642 US gallons.

The UK gallon (imperial gallon) equals exactly 4.54609 liters, about 20% larger than the US gallon, and remains the standard fuel measurement in the United Kingdom and some Commonwealth nations. British fuel efficiency is expressed in miles per imperial gallon, which yields higher numbers than the US equivalent. One UK gallon equals approximately 1.201 US gallons.