Calculate your car's fuel consumption in liters per 100 km (and the equivalent miles per gallon) from the distance traveled and the fuel used.
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Fuel consumption expressed as liters per 100 kilometers (L/100km) is the standard metric-system measure of a vehicle's efficiency: how many liters of fuel it burns to cover a fixed distance of 100 km, meaning a lower number always means better efficiency, since you're using less fuel to travel the same distance. This tool converts your actual trip distance and fuel used, accepting either kilometers or miles and liters or gallons as inputs, into this standardized L/100km figure, and also shows the equivalent U.S.-style miles-per-gallon (MPG) figure, where a higher number means better efficiency — the inverse relationship between the two units (one improves as it decreases, the other improves as it increases) is exactly why converting between them isn't a simple flip of the number, but requires a proper unit conversion calculation that accounts for both the distance-to-volume inversion and the different unit systems involved. How accurate the result is depends heavily on how it's measured: logging a single short trip is skewed by transient conditions like traffic or temperature, while calculating consumption across several consecutive full tanks gives a more representative average of the vehicle's real-world performance, which is why that method is recommended for anyone comparing trips or vehicles over time.
Anyone who has driven in both a metric-system country and the United States has probably noticed something confusing: fuel efficiency numbers seem to work in opposite directions. A more efficient car has a lower L/100km number but a higher MPG number, which trips up plenty of people trying to mentally convert between the two systems on the fly.
The reason traces back to what each unit is actually measuring, and in which order. L/100km asks: given a fixed distance (100km), how much fuel do you need? Less fuel for the same distance is better, so the number should go down for better efficiency. MPG asks the reverse question: given a fixed amount of fuel (one gallon), how far can you travel? Farther on the same fuel is better, so the number should go up for better efficiency.
Because one system measures 'fuel per fixed distance' and the other measures 'distance per fixed fuel,' converting between them isn't a simple linear conversion like converting kilometers to miles — it's a mathematical inversion (dividing into a constant) combined with a unit conversion, which is why a spreadsheet formula or calculator handles it more reliably than mental math, especially for anyone not deeply familiar with both systems.
This distinction matters practically for anyone comparing vehicles across regions or reading foreign car reviews: a European car review quoting '6.5 L/100km' and an American review quoting '36 MPG' for a similar vehicle class are actually describing comparable, though not identical, real-world efficiency — being able to convert between them lets you compare vehicles fairly regardless of which market's marketing materials or reviews you're reading.
For the most reliable real-world reading of your own vehicle's consumption, the most accurate method is measuring over one full tank — filling completely, resetting the trip odometer, driving until the tank is nearly empty, then refilling completely and noting exactly how much fuel went in. Measuring over partial tanks or short trips introduces more error, since fuel pump shutoff points, temperature, and driving conditions vary trip to trip in ways that average out better over a full tank's worth of driving.
L/100km measures fuel consumed per fixed distance (so less fuel for the same distance is better, meaning lower is better), while MPG measures distance traveled per fixed amount of fuel (so more distance from the same fuel is better, meaning higher is better) — they measure the same underlying efficiency from two opposite directions.
It varies widely by vehicle type, but roughly 5-7 L/100km is common for efficient compact/hybrid cars, 8-11 L/100km for typical mid-size sedans and SUVs, and higher for larger trucks and older vehicles.
Yes — measuring fuel consumption over a full tank (from full to full) typically gives a more accurate real-world average than a single short trip, since it smooths out variations from short trips, cold starts, and traffic conditions.