Fuel Economy Converter
Fuel Economy Converter translates L/100km, US mpg, and km/L. Unlike ordinary factor conversion, L/100km is fuel consumption while mpg and km/L express distance per fuel volume, so the relationship is reciprocal. The mpg constant used is 235.214583, corresponding to the US gallon rather than the imperial gallon.
Runs locally — files stay on your deviceWhy does better efficiency lower L/100km but raise mpg?
The measures are reciprocals: one reports fuel per distance, the other distance per fuel.
Consumption and economy point in opposite numeric directions
US mpg = 235.214583 ÷ (L/100km), while km/L = 100 ÷ (L/100km). Zero produces an undefined reciprocal and is rejected.
How it works
The source is first converted to L/100km using reciprocal formulas and then converted to the requested unit.
Key concepts
US and imperial gallons differ
The selected mpg constant is for the US liquid gallon.
Reciprocal conversions are nonlinear
A one-unit change does not have a constant effect across the scale.
When to use it
- Compare US vehicle ratings with metric consumption.
- Translate km/L to L/100km.
- Understand reciprocal fuel metrics.
When not to use it
- Do not use mpg as imperial mpg.
- Do not interpret laboratory ratings as guaranteed real-world consumption.
- Do not enter zero or negative values as physically meaningful economy.
Worked examples
Metric to US mpg
- Input
5 L/100km- Expected output
About 47.0429 mpg
235.214583 ÷ 5.
Kilometres per litre
- Input
20 km/L- Expected output
5 L/100km
100 ÷ 20.
US mpg to metric
- Input
30 mpg- Expected output
About 7.84049 L/100km
The US-gallon constant is divided by 30.
Common mistakes
Using imperial mpg
Imperial gallons are larger. Correction: Use a converter that explicitly supports imperial mpg.
Applying direct multiplication
L/100km and mpg are reciprocal. Correction: Use the stated formulas.
Treating a rating as a prediction
Driving, temperature, load, and test cycle affect actual use. Correction: Label the result as a unit conversion.
Best practices
- Label mpg as US mpg.
- Avoid zero input.
- Separate unit conversion from real-world fuel forecasting.
Related operations and differences
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Length Converter
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Power Converter
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Pressure Converter
Choose Pressure Converter when you need to convert pascals, bar, PSI and atmospheres.; use Fuel Economy Converter specifically for convert.
Limitations and privacy
- US mpg only.
- No imperial mpg, emissions, fuel price, trip, or test-cycle model.
- Zero yields an undefined result.
Values are converted locally in this browser and are not uploaded.
Frequently asked questions
Which gallon does mpg use?
US liquid gallon.
Is a lower L/100km better?
Yes, for fuel consumption.
Is a higher mpg better?
Yes.
Why is zero invalid?
The reciprocal formula would divide by zero.