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 the change in temperature. In the US, the weight of alcoholic and petroleum products is defined as 60°F (16°C).
US Dry Gallon
The US dry gallon is equal to 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