The gallon (gal) is a unit of measuring for measuring liquid capacity. It is used in both US customary and British imperial systems of measurements. There are three different sizes of gallons used today. The imperial gallon is 4.54 liters and common in the Commonwealth states and some Caribbean nations. The US gallon is about 3.785 liters and common in the United States and Latin America. The U.S dry gallon is about 4.405 Litres or 1⁄8 US bushel.

## The Imperial Gallon

The imperial or UK gallon is a unit of measurement exactly 4.54609 liters or 277.42 cubic inches. It is common in the Commonwealth countries and some Caribbean states. The imperial gallon was initially based on 10 pounds which translates to 4.54kg of water at 17 °C. The imperial fluid ounce weighs 1⁄160 of the imperial gallon. An imperial gallon is divided into four quarts, each quart is consisting of two pints, and each pint consists of 20 imperial fluid ounces.

## US Liquid Gallon

One US gallon is defined as 3.7854 liters or 231 cubic inches. At 62°F (17°C), a US liquid gallon of water is equal to 3.78 kgs or 8.34 pounds. It is 16.6% lighter compared to the imperial gallon. However, just like the imperial gallon, a US gallon is divided into four quarts, each quart is divided into two pints, and each pint contains 16 US fluid ounces. Therefore, it takes 128 US fluid ounces to fill a US liquid gallon. It is common to specify the temperature at which the material will weigh or occupy a particular volume. This is done to overcome the change in volume or mass that results from change in temperature. In the US, the weight of alcoholic and petroleum products are defined as 60°F (16°C).

## US Dry Gallon

The US dry gallon is equal to an eight of the Winchester bushel, 268.8025 cubic inches, or 4.4.5 liters.

1 Gallon [Fluid, US] = 3.7854118 Liters

1 Gallon [Dry, US] = 4.4048838 Liters

1 Gallon [UK] = 4.54609 Liters

## Global Usage of Gallons

The imperial gallon was used in the UK until 1994. The fuel economy, in particular, operated on gallons in Canada, the UK, and the US. The EU directive 80/181/EEC effected on December 31, 1994, barred the continued use of the gallon for trading and official purpose in favor of the liter. However, the gallon could still be used as a secondary unit of measurement. On September 30, 1995, the UK amended its legislation and adopted the liter. Several states in the Caribbean and South America are still using the gallon. In 2010, the United Arab Emirates adopted the use of the liter and began selling petroleum products in liters. In 2015 the states of Antigua and Barbuda also switched to the liter.