Fuel efficiency is measured differently depending on which country you are in. The US uses miles per gallon (MPG), most of the world uses km/L or L/100km, and Europe officially reports in L/100km. Here is how they all work and how to convert between them.
The Three Main Units
Miles per Gallon (MPG)
Used in the United States and UK. Higher is better — a car getting 40 MPG is more fuel-efficient than one getting 25 MPG. Note: US MPG uses the US gallon (3.785 L), while UK MPG uses the imperial gallon (4.546 L), so UK MPG values are always ~20% higher.
Kilometres per Litre (km/L)
Used across most of Asia, India, and Latin America. Higher is better — a car getting 15 km/L is more efficient than one getting 10 km/L.
Litres per 100 kilometres (L/100km)
Used in Europe, Australia, and Canada. Lower is better — a car using 6 L/100km is more efficient than one using 10 L/100km. This is the inverse of km/L.
Conversion Formulas
km/L to L/100km: divide 100 by km/L value
MPG (US) to km/L: multiply by 0.4251
L/100km to km/L: divide 100 by L/100km value
Quick Reference Table
| km/L | MPG (US) | L/100km | Efficiency |
|---|---|---|---|
| 7 km/L | 16.5 MPG | 14.3 L/100km | Poor |
| 10 km/L | 23.5 MPG | 10 L/100km | Average |
| 13 km/L | 30.6 MPG | 7.7 L/100km | Good |
| 17 km/L | 40 MPG | 5.9 L/100km | Excellent |
| 21 km/L | 49.4 MPG | 4.8 L/100km | Hybrid |
How to Calculate Your Car's Fuel Efficiency
- Fill up your tank completely and note the odometer reading
- Drive as normal until you need fuel again
- Fill up again and note how many litres it takes
- Calculate: km/L = (distance driven) ÷ (litres used)
Example: 450 km driven, used 35 litres → 450 ÷ 35 = 12.86 km/L