Explanation
Two ways to measure fuel economy
Fuel economy can express consumption for a fixed distance or distance travelled per unit of fuel. Litres per 100 kilometres decreases when efficiency improves; kilometres per litre increases.
Measure a trip
Fill the tank, drive, then fill it again: the litres added are the fuel used over the distance on the trip meter. Enter both and choose litres per 100 km (lower is better) or kilometres per litre (higher is better).
C = 100 × F ÷ D
| C | consumption in litres per 100 km |
|---|---|
| F | fuel used in litres |
| D | distance driven in kilometres |
E = D ÷ F
| E | economy in kilometres per litre |
|---|---|
| D | distance driven in kilometres |
| F | fuel used in litres |
500 km on 40 litres
| Distance driven | 500 |
|---|---|
| Fuel used | 40 |
| Result | 8 |
40 L ÷ 500 km × 100 = 8 L/100 km
Distance travelled per litre
| Distance driven | 600 |
|---|---|
| Fuel used | 40 |
| Result | 15 |
600 km ÷ 40 L = 15 km/L
A lower consumption trip
| Distance driven | 200 |
|---|---|
| Fuel used | 10 |
| Result | 5 |
10 L ÷ 200 km × 100 = 5 L/100 km
Diagram of this result
The trip expressed as fuel per distance and as distance per fuel; one is 100 divided by the other.
Two figures describe the same trip: litres per 100 kilometres and kilometres per litre. The exact numbers are stated in the answer and the steps.
Common mistakes
Do not enter the tank capacity unless that entire volume was consumed. Compare the same route and conditions where possible. Higher L/100 km means more fuel used, while higher km/L means less fuel per distance. This calculator does not accept miles or gallons.
Assumptions and limits
This is the average for one measured trip, not a forecast or a manufacturer rating. Distance and fuel must both be above zero. Electric energy use, fuel price and emissions are not included, and the answer is only as precise as the measurements. Values use 50 internal digits and are rounded to two decimals only for display.
Sources
Natural Resources Canada, understanding fuel consumption ratings: https://natural-resources.canada.ca/energy-efficiency/transportation-alternative-fuels/personal-vehicles/buying-energy-efficient-vehicle/understanding-fuel-consumption-ratings
Why can the two outputs seem to move in opposite directions?
They are reciprocal representations: L/100 km = 100 ÷ (km/L). Improving economy lowers the first and raises the second.