How it’s calculated
Fuel used is distance divided by fuel economy (or distance × L/100 km ÷ 100). Multiply by the price per gallon or liter.
Example: 300 miles at 28 mpg uses 300 ÷ 28 = 10.71 gal. At $3.25/gal the trip costs $34.82, about 11.6¢ per mile.
Real-world economy varies with speed, load, weather, terrain and air conditioning, so treat the result as an estimate.
Frequently asked questions
How do I convert mpg to L/100 km?
L/100 km = 235.21 ÷ US mpg. 28 mpg ≈ 8.4 L/100 km. For imperial mpg use 282.48 ÷ mpg.
Where do I find my car's fuel economy?
Your trip computer, or fill the tank, reset the trip meter, and divide miles driven by gallons at the next fill. EPA ratings are listed on fueleconomy.gov.
Does this include other driving costs?
No, fuel only. Maintenance, tires, depreciation and insurance add substantially to the true cost per mile.
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Sources
- Gas Mileage Tips: Save Money — U.S. Department of Energy / EPA (fueleconomy.gov)
- NIST Handbook 44, Appendix C: Units of Measurement — U.S. National Institute of Standards and Technology
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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