Calculate your gas mileage for your vehicle in miles per gallon. Fill up the gas tank and set your car's trip meter to zero. Drive until it is time to fill up your gas tank again and note the trip meter reading when you fill the gas tank. Divide the number of miles on the trip meter by the number of gallons of gas you purchased to determine your gas mileage rate.
Calculate the length of your trip by determining the number of miles from your present or starting location to your final destination. If your trip will have multiple planned stops, you may consider breaking it into segments and then adding the miles for each segment to find the total mileage. You can determine the mileage for your trip by using city-to-city mileage charts on statewide or maps of the United States or you may consider using a system such as MapQuest. MapQuest allows you to choose “Directions” and then enter your starting and final destination. You can then determine the mileage from one point to another.
Identify representative gas prices between your starting location and your destination. Gas prices fluctuate throughout the United States, so it is beneficial to have an approximate amount for gas costs at different spots along your trip. In order to determine potential gas prices along your travel route, you may consider using GasBuddy, which provides information about gas prices throughout the United States and Canada. You can search for gas prices along your route and find gas stations by searching for the city and state along different parts of your trip.
Average the gas prices you found in Step 3 to find the expected average cost of gas during your trip.
Determine the gas cost estimate for your trip. Divide the total number of miles that you need to travel by the miles per gallon. Take the result and multiply it by the average gas price. This will be the calculated gas expenditure for a trip.
