Gallon

Lore & Background

The gallon originated as the basis of systems for measuring wine and beer in England. The wine gallon (equal in size to the US gallon) and the ale gallon (1.65% larger than the imperial gallon) were different.

Reader's Guide

The gallon remains significant as a unit of volume in both the imperial and US customary systems, though its use has declined in many countries. The imperial gallon continues to be used as the standard petrol unit in four British Overseas Territories and four countries, while the US gallon is used for gasoline in the United States and several other nations. Both gallons are divided into four quarts, eight pints, or thirty-two gills, but the imperial gill is divided into five fluid ounces and the US gill into four, leading to different sizes. The gallon has been removed from the list of legally defined primary units in the European Union, and the UK and Ireland have replaced it with the litre as a primary unit of trade, though it can still be used as a supplementary unit. Miles per imperial gallon is used as the primary fuel economy unit in the UK and as a supplementary unit in Canada. The US dry gallon is no longer used.

Did You Know?

• There are four gills in a pint, two pints in a quart, and four quarts in a gallon.
• The imperial gill is divided into five imperial fluid ounces, while the US gill is divided into four US fluid ounces.
• The US dry gallon, defined as one-eighth of a US Winchester bushel, is no longer used.