A gallon is a unit of volume measurement. There are two main types of gallons:

• The US gallon is defined as 231 cubic inches, which is approximately 3.785 liters.
• The Imperial (UK) gallon is larger, defined as 4.54609 liters.

In the context of gasoline prices in the USA as of August 2025, the average retail price per gallon is about $3.27 for all grades and formulations of gasoline. This price can vary slightly depending on the exact location and grade of gasoline.