MPG Calculator
Calculate your car's fuel economy: enter miles driven and gallons used to get miles per gallon (MPG) and liters per 100 km.
Our free MPG calculator turns two numbers from your fuel receipts — miles driven and gallons used — into your car's real-world fuel economy, in both MPG and metric L/100km. Track it over time to spot a drop that could mean low tire pressure or a needed tune-up.
Fill up, reset the trip odometer, then drive and fill up again.
Gallons it took to refill the tank to full.
How to use this calculator
- Fill your tank to full and reset the trip odometer (or record the odometer reading).
- Drive normally until the tank is nearly empty.
- Fill the tank to full again and note the exact gallons pumped.
- Enter the miles driven and gallons used above and press Calculate.
The formula
MPG = miles driven ÷ gallons used; L/100km = 235.215 ÷ MPG
Worked example
Driving 300 miles on 12 gallons gives 25 MPG, or 9.41 L/100km — about average for a gasoline car.
Frequently Asked Questions
How do I measure my MPG accurately?
Fill your tank completely, reset your trip odometer (or note the odometer reading), and drive normally until the tank is nearly empty. Fill up again to full and note exactly how many gallons it took. Divide the miles driven by the gallons used — that is your real-world MPG. Repeat over a few tanks for an average that smooths out one-off variations.
What is L/100km and how does it relate to MPG?
Liters per 100 kilometers is the metric fuel-economy standard used almost everywhere outside the US. Unlike MPG, where higher is better, a lower L/100km is better because it measures consumption rather than distance. The conversion is L/100km = 235.215 ÷ MPG, so 25 MPG equals about 9.4 L/100km.
What is a good MPG for a car?
For a typical gasoline car, 25–35 MPG is good and anything over 40 is excellent — usually hybrid territory. Large trucks and SUVs often land between 15 and 25 MPG. Compare your result to the EPA rating for your specific model: if you are well below it, check tire pressure, air filter, and driving habits like hard acceleration.
Why is my MPG lower in winter?
Cold weather hurts fuel economy several ways: the engine takes longer to reach efficient operating temperature, winter-blend gasoline contains slightly less energy, tire pressure drops as air contracts, and heaters, defrosters, and heated seats all draw power. A 10–15% winter drop is normal in cold climates.
Does cruise control improve MPG?
On flat highways, yes — cruise control keeps speed steady and avoids the small accelerations that waste fuel, typically saving a few percent. On hilly roads, a skilled driver can beat cruise control by letting speed drift slightly uphill and coasting downhill, but for most people cruise is the more efficient choice.