How fuel efficiency is calculated
Efficiency is the distance covered per unit of fuel burned. The same trip can also be expressed as fuel used per 100 km, a common way fuel economy is labeled outside the US.
- distance — kilometers driven
- fuel — liters of fuel used
- price — price per liter
More detail
km/L vs. L/100km
km/L is easier to compare for a single trip; L/100km is easier to compare across cars because it scales linearly with fuel cost over a fixed distance. A car using 8 L/100km burns twice the fuel of one using 4 L/100km over the same distance.
Practical tip. Fill the tank fully at both the start and end of a measurement period so the fuel-used figure reflects only the distance you tracked, not a partial tank.
Frequently asked questions
How do I calculate fuel efficiency in km/L?
Divide distance driven by fuel used: 500 km on 40 L gives 12.5 km/L. Enter your own distance and fuel-used values above for the exact figure.
What's the difference between km/L and L/100km?
km/L tells you how far one liter takes you; L/100km tells you how much fuel a fixed 100 km trip burns. A car at 12.5 km/L uses about 8 L/100km — L/100km scales linearly with cost, making it easier to compare cars.
How is total fuel cost calculated?
Fuel cost = fuel used × price per liter. At ₩1,700/L, filling 40 L costs ₩68,000.
Why does my real-world fuel efficiency differ from the spec sheet?
This is a simple ratio of distance to fuel used, so it reflects your actual driving — real efficiency varies with driving style, terrain, load, and vehicle condition, which the spec-sheet number doesn't capture.