US Gallons (Liquid)
Abbreviation/Symbol:
US gal
gal (liquid)
Unit of:
Worldwide use:
The US gallon is what petrol and milk are sold by in the United States. Outside it, it turns up mostly in the oil trade, where a barrel is defined as 42 US gallons.
Definition:
The US gallon is 231 cubic inches, or about 3.785 liters. It is the old English wine gallon, which the US kept: Britain replaced its gallons in 1824 with the British imperial gallon, so the UK gallon is now larger at 4.546 liters.
Origin:
The US gallon is the old English wine gallon, fixed at 231 cubic inches under Queen Anne in 1707. Britain left it behind in 1824 with the imperial gallon, defined as the volume of 10 pounds of water, and the two have differed ever since.
Usage context:
In the US, fuel and milk are sold by the gallon, and fuel economy is quoted in miles per gallon. To turn that into liters per 100 kilometers, divide 235 by the mpg figure – 30 mpg is about 7.8 liters per 100 kilometers. UK mpg uses the larger imperial gallon, so divide 282 instead.