What Is a Fuel Consumption Converter?
It converts between fuel economy (distance/volume) and fuel consumption (volume/distance) units using reciprocal logic and exact gallon/liter definitions.
For volume units, see the Volume Converter. For speed, see the Speed Converter. For engine power ratings, see the Horsepower Converter.
How to Use the Fuel Consumption Converter
- 1Enter a fuel efficiency value greater than 0.
- 2Select from and to units (economy or consumption).
- 3Click Convert — results scroll into view with km/L, L/100 km, mpg US, and mpg UK equivalents.
- 4Watch for the US vs UK gallon note when crossing mpg systems.
- 5Use presets for common mpg ↔ L/100 km conversions.
Fuel Economy vs Fuel Consumption
Consumption = volume / distance. They are inverses — high mpg is good; high L/100 km is bad.
km/L and L/100 km
Example: 20 km/L = 5 L/100 km.
mpg US, mpg UK, and Gallon Difference
1 US gal = 3.785411784 L exactly. 1 UK gal = 4.54609 L exactly. Same physical efficiency gives higher mpg UK than mpg US. Nautical consumption units (gal/nmi) are also supported.
mpg vs L/100 km Comparison
| mpg (US) | L/100 km | km/L |
|---|---|---|
| 20 | 11.76 | 8.50 |
| 30 | 7.84 | 12.75 |
| 40 | 5.88 | 17.01 |
| 50 | 4.70 | 21.26 |
Common Conversion Formulas
L/100 km = 282.4809363 / mpg UK. Constants derive from mile and gallon definitions.
How to Read Results
mpg and km/L: higher is better. L/100 km and gal/100 mi: lower is better. Always compare after converting to the same unit.
Real-World Factors
Actual fuel use depends on speed, traffic, terrain, load, tire pressure, driving style, and fuel type. Lab ratings differ from real-world consumption.
Examples
30 mpg US
30 mpg US ≈ 7.84 L/100 km.
20 km/L
20 km/L = 5 L/100 km.
50 mpg UK
50 mpg UK ≈ 5.65 L/100 km.
Common Mistakes
Assuming mpg US = mpg UK. Thinking higher L/100 km is better. Comparing mpg to L/100 km without converting. See the Volume Converter for gallon/liter volume conversions.
Limitations
Converts units only; does not predict real-world fuel use or cost without additional inputs.
FAQ
How do you convert km/L to L/100 km?›
L/100 km = 100 / km/L. Example: 20 km/L = 5 L/100 km.
How do you convert mpg US to L/100 km?›
L/100 km = 235.214583 / mpg US. Example: 30 mpg ≈ 7.84 L/100 km.
Is mpg US the same as mpg UK?›
No. The imperial gallon is larger, so mpg UK is numerically higher for the same efficiency.
Why is lower L/100 km better?›
L/100 km measures fuel used per distance — less fuel per 100 km means better efficiency.
How do I convert km/L to mpg?›
mpg US = 235.214583 / L/100 km, or convert km/L to L/100 km first (100/km/L), then apply the mpg formula.
How do you convert mpg UK to L/100 km?›
L/100 km = 282.4809363 / mpg UK. Example: 50 mpg UK ≈ 5.65 L/100 km.
What is L/100 mi?›
Liters per 100 miles — a consumption unit (lower is better) using metric volume and statute miles. Useful when comparing US road distances with metric fuel volume.
What is gal/100 mi?›
US gallons per 100 miles — a consumption unit (lower is better). Related to mpg by: mpg US = 100 / (gal/100 mi).
What fuel units do ships use?›
Marine efficiency often uses liters or gallons per nautical mile (L/nmi, gal/nmi) or nautical miles per gallon. This converter includes nmi/L and gal/nmi variants.
Does this converter predict real-world fuel use?›
No. It converts between efficiency units only. Actual consumption depends on speed, load, terrain, driving style, and fuel type.
Sources
Author & technical reviewer
Manish Kumar
PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.
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