Fuel Efficiency Calculator
Calculate your vehicle fuel efficiency in MPG or km/L.
Enter distance driven and fuel used to find out how efficient your car really is.
Fuel efficiency measures how far a vehicle travels per unit of fuel. It is expressed as miles per gallon (MPG) in the US and UK, or liters per 100 km (L/100km) across most of the rest of the world.
The core formulas:
MPG = Miles Driven / Gallons Used
km/L = Kilometers Driven รท Liters Used
L/100km = (Liters Used รท Kilometers Driven) ร 100
Note on which metric unit this page uses. Selecting metric here returns km/L, where higher is better, the same direction as miles per gallon. Most of Europe instead quotes L/100km, where lower is better. The two are reciprocals scaled by 100: L/100km = 100 รท km/L. So 12 km/L is 8.3 L/100km. If you are used to reading fuel economy the European way, remember the number on this page moves the opposite direction from the one on your dashboard.
Converting between the two:
L/100km = 235.21 / MPG (US gallons)
MPG = 235.21 / L/100km
What each variable means:
- Miles/km Driven โ measure from your odometer at fill-up: end reading minus start reading
- Gallons/Liters Used โ exactly what it took to fill the tank back to full each time
Worked example: You fill up when the odometer reads 24,850 miles. You drove since the last fill-up (at 24,210 miles) and used 21.4 gallons.
Miles driven = 24,850 โ 24,210 = 640 miles MPG = 640 / 21.4 = 29.9 MPG
That converts to 235.21 รท 29.9 = 7.9 L/100km, or 12.7 km/L.
One tank is not a measurement. Any single fill-up carries the error of how hard the pump clicked off, and auto-shutoff varies by a half gallon between stations. It also carries whatever that particular tank was spent on: a week of short cold-start commutes can read 20% worse than the same car on one highway run. Average three or four consecutive fill-ups before you believe a number, and never compare a summer tank against a winter one. Cold air is denser, winter fuel blends carry slightly less energy, and the engine spends longer in warm-up enrichment, so a 10% seasonal drop is normal and is not a fault.
To turn the figure below into money per month, use the Fuel Cost Calculator, which takes your pump price and monthly mileage.
Fuel economy ratings from the EPA (Environmental Protection Agency), 2024 US averages:
- Compact car: 28โ36 MPG combined
- SUV/crossover: 22โ30 MPG combined
- Full-size pickup: 16โ22 MPG combined
- Hybrid sedan: 45โ55 MPG combined
- Plug-in hybrid: 40โ60 MPG (gas mode)
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.