Calculators & everyday math
MPG vs. Liters per 100 km: Converting Fuel Economy
Miles per gallon and liters per 100 kilometers both describe fuel economy, but they measure it from opposite directions. MPG counts how far a vehicle goes on a fixed amount of fuel; L/100 km counts how much fuel it uses over a fixed distance. That is why converting between them takes a division rather than a multiplication.
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Two opposite measurements
The US uses miles per US gallon. Canada, Europe, Australia, and much of the world use liters per 100 km, and the UK still quotes MPG in imperial gallons.
- MPG (distance per fuel): higher is better.
- L/100 km (fuel per distance): lower is better.
- Doubling MPG halves L/100 km.
The conversion formula
With a mile of exactly 1.609344 km and a US gallon of exactly 3.785411784 liters, the constant works out to 235.2145833: L/100 km = 235.2145833 ÷ MPG (US), and MPG (US) = 235.2145833 ÷ L/100 km. The same number works in both directions because each unit is the reciprocal of the other, scaled.
MPG (US) to L/100 km
| MPG (US) | L/100 km |
|---|---|
| 15 | 15.68097222 |
| 20 | 11.76072917 |
| 25 | 9.408583333 |
| 30 | 7.840486111 |
| 35 | 6.720416667 |
| 40 | 5.880364583 |
| 50 | 4.704291667 |
L/100 km to MPG (US)
| L/100 km | MPG (US) |
|---|---|
| 4 | 58.80364583 |
| 5 | 47.04291667 |
| 6 | 39.20243056 |
| 8 | 29.40182292 |
| 10 | 23.52145833 |
| 12 | 19.60121528 |
A quick mental estimate
Divide 235 by either number. 235 ÷ 25 MPG is about 9.4 L/100 km, and 235 ÷ 7 L/100 km is about 33.6 MPG. For UK imperial MPG, use 282 instead.
MPG vs. L/100 km FAQ
- What is 40 MPG in L/100 km?
- About 5.88 L/100 km (5.880364583).
- What is 5 L/100 km in MPG?
- About 47.04 US MPG, or about 56.5 UK imperial MPG.
- Why can’t I just multiply by a factor?
- Because the units are inverted: one is distance ÷ fuel and the other is fuel ÷ distance. Converting means dividing a constant by your value.
- How does km/L fit in?
- Kilometers per liter is distance per fuel, like MPG. Divide 100 by km/L to get L/100 km: 12.5 km/L is 8 L/100 km.
- Does the formula work for UK MPG?
- Not with the same constant. For imperial MPG use 282.4809363: L/100 km = 282.4809363 ÷ MPG (Imperial/UK).
Related guides
- US vs. UK MPGWhy the same car gets about 20% more miles per imperial gallon than per US gallon, how to convert between them, and how to tell which one you have.
- Why Lower L/100 km Is BetterFuel per distance versus distance per fuel, the MPG illusion, and why liters per 100 km makes fuel savings easier to compare.
Open the tool
Jump into Fuel Economy Converter when you are ready to process your files.
