Car fuel economy calculator (km/l)
Find out your car's real fuel economy in km/L and L/100 km from distance driven and liters filled. Example: 420 km on 35 liters gives 12 km/L.
Fill the tank, reset the trip, and at the next fill-up note the km and liters.
How the calculation works
Fuel economy tells how many kilometers the car does per liter:
economy (km/l) = distance driven ÷ liters used
Higher is better. To measure yours, fill the tank, reset the trip meter and, at the next fill-up, divide the km driven by the liters it took.
Step-by-step example
Drove 420 km and needed 35 liters to refill:
- Economy: 420 ÷ 35 = 12 km/l
City vs highway
City economy is lower (more stop-and-go); highway is higher (steady speed). That's why makers quote both.
Examples
- 600 km on 40 L: 15 km/l (good highway figure).
- 300 km on 30 L: 10 km/l (typical city figure).
Frequently asked questions
What is good fuel economy?
Compact cars do ~10–14 km/l in the city and more on the highway.
How to convert km/l to mpg?
Multiply km/l by about 2.352. E.g. 12 km/l ≈ 28 mpg.
What hurts fuel economy most?
Speeding, under-inflated tires, heavy AC use, extra weight and stop-and-go traffic. Smooth driving saves the most.
How do I convert km/L to L/100 km?
Divide 100 by the km/L figure. A car doing 12 km/L uses 8.3 L per 100 km.
Why is my mileage worse than the manufacturer's?
Official figures come from standardised lab cycles without traffic or air conditioning. Real-world gaps of 10–20% are normal.
Is the trip computer reliable?
It is fine for trends but usually optimistic by a few percent. For the real figure, measure full tank to full tank.
What does each kilometre cost?
Divide fuel price by mileage: at R$6.20 and 12 km/L, that is R$0.52 per km — fuel only, before depreciation, insurance and maintenance.
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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources