A US liquid gallon is equal to 3.785 liters or 0.833 UK gallons in the metric system.However, the size of a gallon varies depending on the type of gallon used: Definition of GallonsĪ gallon is defined as a unit of liquid capacity in both the US customary and imperial systems of measurement.

They are also different from barrel of oil equivalent (BOE), which is a unit of energy based on the approximate energy released by burning one barrel of crude oil. They are also different from liters, which are a larger unit of volume. They are different from cups, which are a smaller unit of volume. They are also used to measure some dry goods, such as grains, fruits, nuts, etc. Gallons are a unit of volume that are used to measure liquids, such as water, milk, oil, wine, etc. Quart (qt) is a unit of Volume used in Standard system. Gallon (gal) is a unit of Volume used in Cooking system.