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Fuel efficiency units don't convert by a simple multiplication factor the way most units do — MPG and km/L measure distance per unit of fuel (higher is better), while L/100km measures fuel per unit of distance (lower is better), an inverse relationship that a naive linear conversion would get wrong.
This converter correctly handles that inverse relationship between MPG (US/UK), km/L, and L/100km.
How it works
Enter a fuel efficiency value and choose the units to convert from and to. The converter first converts your value to L/100km (a true consumption measure), then converts from that base to your target unit, correctly applying the inverse relationship at each step.
- Enter value.
- Enter from.
- Enter to.
- Click Calculate to see your results.
Examples
30 MPG (US)
A vehicle getting 30 MPG (US) uses about 7.84 liters per 100 kilometers — a lower L/100km number means better efficiency, the opposite direction from MPG.
Who should use it
- Comparing a US-market vehicle's MPG rating to a European L/100km figure.
- Converting a fuel efficiency figure for an international road trip cost estimate.
Industry applications
- Automotive and transportation
- International vehicle specifications and comparisons
Advantages
- Correctly handles the inverse relationship between consumption and efficiency units.
- Supports both US and UK gallon-based MPG separately.
Limitations
- Doesn't account for real-world driving condition differences (highway vs. city) — this converts stated efficiency figures directly.
Common mistakes to avoid
- Treating MPG and L/100km as if they convert with a simple multiplication factor, rather than an inverse relationship.
- Mixing up US and UK gallon-based MPG figures, which differ by about 20% for the same actual fuel efficiency.
Best practices
- When comparing vehicle fuel efficiency figures from different countries, always confirm which MPG definition (US or UK) is being used before converting or comparing.
Tips
- When comparing vehicles, remember that fuel savings from efficiency improvements are non-linear in L/100km terms — going from 40 to 20 MPG wastes far more fuel over a fixed distance than going from 20 to 10 MPG saves, a common perception gap known as the "MPG illusion."