How can one calculate car gas mileage?

Calculating the gas mileage of a vehicle can be done either by filling a tank and then manually tracking the distance traveled after filling up, or by resetting the car's trip meter and tracking the distance traveled using that filled tank.

In order to get an accurate reading on the calculation a user must also record how many gallons it takes to fill a car's gas tank. After filling up, drive until the car's tank is empty again; you can then see how many miles were driven and divide that by the number of gallons that were in the car's tank. For instance, if a tank holds 9.5 gallons and the driver went 250 miles on that tank, the miles per gallon is 250 divided by 9.5 or about 26.3 miles per gallon.