Estimate the travel distance with available online tools, such as MapQuest or Google Maps. For example, if you're traveling from Chicago to Toledo, Ohio, the distance is about 250 miles.
Refer to your car’s manual or car dealer information to find out the average gas mileage of your car. The gas mileage is typically given as miles per gallon (MPG). For example, your fuel efficiency may be 25 MPG for your car.
Divide the travel distance by the gas mileage to calculate the amount of gasoline needed for your trip. In this example, it is 250 / 25 = 10 gallons.
Refer to the table "Weekly Retail Gasoline Prices" put out by the U.S. Energy Information Administration to find out current gas prices for your region. For example, the average gas price in Midwest might be $3.55 per gallon.
Multiply the amount of gasoline needed for the trip by the price to figure out the fuel costs. In this example, the fuel cost is 10 gallons x $3.55 per gallon = $35.50.
