Gas Mileage Calculator – What's the Fuel Efficiency?

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On this page is a fuel efficiency or gas mileage calculator, which lets you estimate what fuel efficiency a vehicle achieved by entering some details about a trip. Simply enter how far the vehicle drove, flew, or otherwise traveled and the number of gallons it used over the trip and we'll do the rest. Use either a series of odometer readings or your total number of miles driven.

Gas Mileage Calculator

Using the Gas Mileage Calculator

The gas mileage calculator needs to know how far you drove and how much gas you used, but there are two ways to gather the information. Using the blue toggle below the tool, select your preferred way to enter data:

  • Use Odometer Readings
  • Use Miles Driven

Gas Mileage Based on Two Odometer Readings

To determine your fuel efficiency based on odometer readings, you have to enter three inputs:

  • Odometer Reading 1 - Enter either your odometer reading before or after the trip.
  • Odometer Reading 2 - Enter the opposite odometer reading – before or after the trip – based on your entry in Odometer Reading 1.
  • Gallons of Gas Used - Enter how many gallons of gas you put into your vehicle during the trip, and to return it in the same gas state (see note below).

Gas Mileage Based on Miles Driven

For us to make an estimate about how efficient your vehicle is based on distance and fuel added, you need to enter in a mere two inputs:

  • Miles driven - Enter how long your trip was, including any side excursions you made along the way.
  • Gallons of Gas Used - Enter how many gallons of gas you put into your vehicle during the trip, and returning it to the same gas state (see note below).

Note: For best results, you should compute the fuel you added to return to the same tank state. For example, if you start with a full tank, then fill the tank again when the trip is over and add that amount to the total of gallons you used.

Gas Mileage Calculator Outputs

Once you're happy with the above inputs in whichever style of entry you use, hit the "Calculate Gas Mileage" button.

  • Calculated Gas Mileage - Based on your inputs, our estimate of the efficiency of your vehicle. Nominally, this is in miles per gallon.

Hope it was a Great Trip!

I'm happy you found our tool, and I hope it was useful in calculating how efficient your vehicle was over a trip. For more calculators covering cars, trucks, vans, and things that fly or float, see the following tools:



PK started DQYDJ in 2009 to research and discuss finance and investing and help answer financial questions. He's expanded DQYDJ to build visualizations, calculators, and interactive tools.

PK lives in New Hampshire with his wife, kids, and dog.

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