420 km on 28 litres
- Distance covered
- 420 km
- Fuel used
- 28 L
- A second leg, distance
- 0 km
- A second leg, fuel
- 0 L
- Fuel price a litre
- ₹105
- Claimed efficiency
- 20 km/L
Efficiency15
420 / 28
Open this exampleEverydayvehicle
Fuel Efficiency Calculator
Fuel efficiency from distance and fuel used, across two legs if you have them, in all four units. Combining legs by averaging their kmpl figures is wrong, and the page shows both answers so the size of the error is visible.
Also called: mileage calculator, kmpl calculator.
Efficiency
15
15 km a litre, which is 6.67 litres per hundred kilometres and costs ₹7 a kilometre. That is 25% below the claimed 20 km a litre. Ten to twenty percent short is normal, because the test cycle is gentler than real traffic. In litres per hundred kilometres that is 6.67, the unit that can be averaged across legs. Kilometres per litre cannot, which is why a second leg is worth entering separately.
Litres per 100 km
6.67
Miles a gallon, US
35.28
Miles a gallon, imperial
42.37
Cost a kilometre
₹7
Against the claimed figure
-25%
What averaging the two legs directly would give
0
Against the claim
That is 25% below the claimed 20 km a litre. Ten to twenty percent short is normal, because the test cycle is gentler than real traffic.
On averaging
In litres per hundred kilometres that is 6.67, the unit that can be averaged across legs. Kilometres per litre cannot, which is why a second leg is worth entering separately.
The same efficiency in other units
| Unit | Value | Used in |
|---|---|---|
| Kilometres a litre | 15 | India and much of Asia |
| Litres per 100 km | 6.67 | Europe, and the only one that averages |
| Miles a gallon, US | 35.28 | United States |
| Miles a gallon, imperial | 42.37 | United Kingdom |
Method and background
How this is calculated
Efficiency is total distance over total fuel, full stop. Averaging the efficiency of two legs gives a different and wrong answer, because kilometres per litre is a reciprocal: the leg where the car did badly used more fuel and therefore deserves more weight, which a simple average does not give it. Litres per hundred kilometres has the opposite property and can be averaged safely, which is why most of Europe quotes it. Against a manufacturer figure, a shortfall of ten to twenty percent is normal, since the test cycle is gentler than real traffic.
total distance over total fuel, which is the only correct way to combine legs- d
- Distance
- f
- Fuel
Worked examples
Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
two legs combined correctly
- Distance covered
- 100 km
- Fuel used
- 10 L
- A second leg, distance
- 100 km
- A second leg, fuel
- 5 L
- Fuel price a litre
- ₹105
- Claimed efficiency
- 0 km/L
Efficiency13.33
boundary: 200 km on 15 litres is 13.33, where averaging 10 and 20 gives 15
Open this exampleMethod and limits
What it assumes
- A full-to-full measurement, which is the only reliable way to know the fuel used.
What it deliberately does not model
- A single tank is a noisy sample, since the fill level and terrain both vary.
- Manufacturer figures come from a standardised cycle and are not a promise about real driving.
Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator
Frequently asked questions
- Why is my mileage below the claimed figure?
- Because the test cycle is gentler than real traffic. Ten to twenty percent below the rated figure is normal, and city driving with air conditioning can be further off again.