The US gallon is a unit of volume used in the United States customary system. It is defined as 3.78541 liters.
The term "gallon" dates back to the 14th century, originally used in England. The US gallon was established in 1824, based on the British wine gallon, which was set at 231 cubic inches. In 1976, the US adopted the metric definition of the gallon, aligning it with 3.78541 liters.
The US gallon is commonly used in everyday life for measuring liquid volumes, such as gasoline, milk, and water. It is also used in cooking and food service. In science and engineering, it is often employed for fluid measurement in the US.