Quick answer: km/L and L/100 km are reciprocals: km/L = 100 ÷ (L/100 km), so 8 L/100 km = 12.5 km/L.
How it's calculated
km/L and mpg measure distance per fuel (higher is better); L/100 km measures fuel per distance (lower is better). To go between them, divide 100 by the figure.
1 mpg (US) = 1.609344 km ÷ 3.785411784 L = 0.4251 km/L; 1 mpg (UK) = 1.609344 km ÷ 4.54609 L = 0.3540 km/L. A UK mpg figure is about 20% higher than the US figure for the same car.
To estimate what a trip costs in fuel, multiply the distance by L/100 km, divide by 100, then multiply by the price per litre.
Worked examples
- A car using 8 L/100 km: 8 L/100 km = 12.5 km/L
- 15 km/L in L/100 km: 15 km/L = 6.667 L/100 km
- 30 mpg (US): 30 mpg US = 12.75 km/L
Common fuel economy conversions
| From | To |
|---|---|
| 5 L/100 km | 20 km/L |
| 6 L/100 km | 16.67 km/L |
| 8 L/100 km | 12.5 km/L |
| 10 L/100 km | 10 km/L |
| 12 L/100 km | 8.333 km/L |
| 8 L/100 km | 29.4 mpg US |
| 10 km/L | 23.52 mpg US |
| 15 km/L | 6.667 L/100 km |
| 30 mpg US | 7.84 L/100 km |
| 40 mpg UK | 7.062 L/100 km |
Frequently asked questions
How do I convert L/100 km to km/L?
Divide 100 by it. 8 L/100 km = 100 ÷ 8 = 12.5 km/L.
Is UK mpg the same as US mpg?
No. The UK gallon is larger (4.546 L vs 3.785 L), so the same car shows a higher UK mpg.
What is good fuel economy?
Many small petrol cars use 5 to 7 L/100 km (14 to 20 km/L); large SUVs often use 10 to 14 L/100 km. Check the official figure for your model.
How do I convert mpg to L/100 km?
Divide 235.2 by US mpg, or 282.5 by UK mpg. A car doing 30 US mpg uses 7.84 L/100 km.
Why is L/100 km better for comparing cars?
Because the savings add up directly. Going from 10 to 8 L/100 km saves 2 litres every 100 km, plain and simple. With km/L or mpg, the same jump saves less the higher you start, which makes comparisons misleading.
Which unit is used in Saudi Arabia?
The Saudi fuel economy sticker on new cars shows km/L, while plenty of European brands quote L/100 km. Convert one into the other before you compare.