Determine how many miles you will be traveling. Visit a mapping/directions website like mapquest or googlemaps to calculate the distance of your trip. Enter your starting city and ending city into the website to determine the distance in miles you'll be traveling, then write down how many miles total it is from point to point.
Calculate how much gas you'll need for your trip. Divide the total miles by your car's miles-per-gallon rate (MPG) to determine how many gallons of gas you need for the road trip. If you don't know your car's MPG, check the owner's manual or make a note of the odometer setting and how many gallons of gas you purchase the next time you fill your car with gas. Drive the car until it needs to be filled up again, then write down the number on the odometer. Divide the number of gallons of gas you bought by the current reading on the odometer. This is your MPG.
Check the average cost of gas in the places you plan on visiting. Monitor the cost of gas utilizing online tools such as AAA's daily fuel gauge report or GasBuddy.com.
Multiply the total gallons of gas you need for the trip by the average gas price. Alternatively, you can plug in the number of miles, your car's MPG and average gas price in Road Trip America's fuel calculator to automatically calculate the cost.
