Full form of USG is United States Gallon (liquid = 231 cu. in. = 3.785411784 litres; dry = 268.8025 cu. in. or 4.40488377086 litres)

The United States Gallon (USG) is a unit of volume measurement commonly used in the United States, particularly for liquid substances. One USG is equivalent to 231 cubic inches or approximately 3.785 liters, making it a crucial metric in industries such as automotive, agriculture, and beverage production. The measure is distinct from the Imperial gallon used in the United Kingdom, which is larger. When dealing with dry substances, the USG translates to about 268.8025 cubic inches or roughly 4.405 liters. The USG is essential for both consumers and industries, as it standardizes the measurement of liquid volumes, ensuring consistency in commerce and trade. This unit is particularly significant in the context of fuel economy, where vehicle efficiency is often expressed in miles per gallon (mpg) using the USG as the standard measure.