How Much Gas Will You Use on Your Road Trip?

By: Clint Pumphrey  | 

Calculating the Cost of Gas for a Road Trip

pumping gas
Nothing can ruin a road trip like pain at the pump, but there are ways to plan ahead and save money. Pramote Polyamate/Getty Images

The cost of gas on a long road trip these days is going to be, well, a lot; there's no way around it unfortunately. But you can calculate a rough estimate of what to expect ahead of time with apps that will do the math for you.

Before you can determine the cost of gas for your road trip, you need to figure out your vehicle's gas mileage. Typically, this number is listed in your owner's manual or online. If you can't find it, you can calculate it yourself by first filling up the tank and resetting the trip odometer. Once you've used at least half of the gasoline in the tank, fill the tank again and note how much fuel you put in the car, as well as the mileage on the odometer. Then divide the number of miles by the gallons of fuel to get your vehicle's miles per gallon (mpg) rating. For example, if you traveled 250 miles (402 kilometers) on 10 gallons (37.8 liters) of gasoline, your car's mpg rating is 25 (kmpl 10.6).


Once you know your car's mpg, you can calculate the amount of fuel you'll need on your road trip. First, find out how many miles you plan to drive by entering your starting and ending points into an online maps program like MapQuest or Google Maps. Then divide this mileage figure by your car's mpg rating to find out how many gallons of fuel you'll need on your trip. For instance, if you plan to drive 500 miles (804.6 kilometers) in a car that gets 25 mpg (10.6 km/l), you'll need about 20 gallons (76 liters) of gasoline.

To find out your total fuel cost, visit a site like GasBuddy. It lists prices for gas stations by brand, city and state so you can determine the average gas prices on the route you'll be driving. Multiply the number of gallons you need times the average gas price to get an idea of what your total fuel cost will be. For example, if gas is about $3.50 a gallon in your area and you need 20 gallons to drive your trip distance, you'll pay $70 for gasoline.

Several online calculators make this even easier, including AAA's Fuel Cost Calculator, which allows you to select your departure and arrival cities, as well as the make and model of your car. It then uses the current average price of gasoline in the areas in which you plan to drive to calculate your total fuel cost. GasBuddy has a similar feature, but its calculator can actually schedule your fuel stops based on the lowest gas prices along your route. With these tools, you'll never be surprised when it comes time to fuel up.

Originally Published: Jun 30, 2011

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More Great Links


  • American Automobile Association. "From Sea to Shining Sea: AAA Predicts 47.9 Million People Will Travel This July 4th." June 21, 2022. (July 11, 2022)
  • Environmental Protection Agency. "Driving More Efficiently." July 7, 2011. (July 11, 2022)
  • Environmental Protection Agency. "Keeping Your Car in Shape." July 7, 2011 (July 11, 2022)
  • Duvauchelle, Joshua. "How to Calculate Gas Mileage for a Trip." USA Today Travel. 2011. (July 10, 2011)
  • GasBuddy. "Gas Price Decline Accelerates, Steepest Since Pandemic Began." July 11, 2022. (July 11, 2022)
  • Higgins, Michelle. "13 Ways to Save on Gas This Summer." The New York Times. May 11, 2011. (July 10, 2011)
  • Roberts, Amy. "Save Gas on Your Next Road Trip." Good Housekeeping. June 29, 2011. (July 10, 2011)
  • Valdes-Dapena, Peter. "Gas Saving Road Trip Tips." CNN Money. April 22, 2008. (July 10, 2011)