Fuel Efficiency Converter
Convert fuel economy between US MPG, UK MPG, litres per 100 km, and km per litre.
Fuel Efficiency Reference
| US MPG | UK MPG | L/100km | km/L |
|---|---|---|---|
| 20 | 24.0 | 11.76 | 8.50 |
| 25 | 30.0 | 9.41 | 10.62 |
| 30 | 36.0 | 7.84 | 12.75 |
| 35 | 42.0 | 6.72 | 14.87 |
| 40 | 48.0 | 5.88 | 17.00 |
| 50 | 60.1 | 4.70 | 21.25 |
Frequently Asked Questions
What is the difference between US MPG and UK MPG?
The US gallon is 3.785 litres, while the UK (imperial) gallon is 4.546 litres — about 20% larger. So a car rated at 40 US MPG gets approximately 48 UK MPG for the same trip. Always check which gallon standard is being used when comparing fuel economy figures.
How do I convert MPG to L/100km?
For US MPG: L/100km = 235.215 ÷ MPG. For UK MPG: L/100km = 282.481 ÷ MPG. Note that MPG and L/100km are inversely related — a higher MPG is more fuel-efficient, while a lower L/100km is more fuel-efficient.
Is lower or higher L/100km better?
Lower L/100km is better — it means the vehicle uses fewer litres of fuel per 100 kilometres driven. A car using 6 L/100km is more fuel-efficient than one using 10 L/100km.
What is a typical fuel efficiency for a modern car?
A typical modern passenger car achieves 7–10 L/100km (28–34 US MPG) in combined city/highway driving. Fuel-efficient hybrids and EVs can achieve 4–6 L/100km equivalent (40–60 US MPG) or better.
How does driving speed affect fuel efficiency?
Most vehicles achieve peak fuel efficiency between 80–100 km/h (50–62 mph). Above this range, aerodynamic drag increases exponentially. Driving at 120 km/h can use 20–30% more fuel than at 90 km/h. City driving with frequent stops and starts is typically less efficient than steady highway driving.