Pro Calculators and Guides
How to Convert Fuel Economy: km/l, L/100km, mpg (US) and mpg (UK)
Understand fuel economy units and convert between km per litre, litres per 100 km and US and UK miles per gallon.
Saizul Amin15 Oct 2026 · Updated 17 Oct 2026 · 1 min read
A car review in the UK quotes mpg, a Bangladeshi dealer quotes km/l, a European brochure lists L/100km. They all describe the same thing in different units, and one of them runs "backwards".
Quick answer
Enter a value and its unit to see the rest. Higher km/l and mpg mean better economy, but lower L/100km is better.
The relationships
- L/100km = 100 ÷ km/l. 12.5 km/l = 8 L/100km.
- mpg (US) = km/l × 2.352. 12.5 km/l ≈ 29.4 mpg (US).
- mpg (UK) = km/l × 2.825. 12.5 km/l ≈ 35.3 mpg (UK).
The UK gallon (4.546 L) is bigger than the US gallon (3.785 L), so a UK mpg figure looks about 20 percent higher.
Quick reference
| km/l | L/100km | mpg (US) | mpg (UK) |
|---|---|---|---|
| 8 | 12.5 | 18.8 | 22.6 |
| 10 | 10 | 23.5 | 28.2 |
| 12 | 8.3 | 28.2 | 33.9 |
| 15 | 6.7 | 35.3 | 42.4 |
| 20 | 5 | 47.0 | 56.5 |
Steps
- Select the unit you have.
- Type the value.
- Read all four units at once.
Tips
- When comparing cars from different sources, check which gallon is used.
- Real-world economy is usually 10 to 25 percent worse than the brochure figure.
- To estimate trip cost, use the trip cost calculator.
