The U.S. gallon is a unit of volume commonly used in the United States, primarily for measuring liquids. It is defined as equal to 128 fluid ounces or approximately 3.785 liters. The U.S. gallon is part of the U.S. customary system of measurement, which is different from the metric system used in many other countries. In contrast to the imperial gallon, which is used in the United Kingdom and is larger at about 4.546 liters, the U.S. gallon is specifically tailored for American usage. This unit is often seen in contexts like fuel sales, cooking, and beverage packaging.