Fuel Economy Converter
Convert fuel economy between consumption (L/100km) and efficiency (mpg, km/L) units.
From
To
- 1
Convert to the base unit
235.214583 - 2
Convert to the target unit
235.214583 L/100km
1 mpg (US) =
| Liters per 100 km | 235.214583 L/100km |
| Kilometers per liter | 0.425144 km/L |
| Miles per gallon (UK) | 1.20095 mpg (UK) |
Formula
How this is calculated
Fuel economy is measured in two opposite ways, so this tool converts through a single base unit: liters per 100 kilometers (L/100km). Consumption units (L/100km) say how much fuel a fixed distance costs, where lower is better; efficiency units (km/L, mpg) say how far a fixed amount of fuel takes you, where higher is better. Because these are reciprocals, the converter divides rather than multiplies — it never uses a simple linear scale factor.
Each unit defines a constant C such that value = C / (L/100km), and inversely L/100km = C / value. The constants come from unit definitions: km/L uses C = 100 (100 km per liter pivot); US mpg uses C = 235.214583 and UK mpg uses C = 282.480936, derived from miles-per-mile and the differing US versus imperial gallon volumes. So US and UK mpg are not interchangeable.
Conversion runs in two steps: the input is mapped to L/100km, then L/100km is mapped to the target unit. Zero, negative, or non-finite inputs return no result to avoid dividing by zero, since infinite economy is not physically meaningful.
About this calculator
Fuel economy can be expressed two ways. Consumption units like liters per 100 kilometers (L/100km) measure how much fuel is used over a fixed distance — lower is better. Efficiency units like miles per gallon (mpg) or kilometers per liter measure how far you travel per unit of fuel — higher is better. The two are inversely related, which is why this converter uses reciprocal functions rather than simple multiplication.
The base unit is L/100km. To convert, km/L = 100 / (L/100km), US mpg = 235.214583 / (L/100km), and UK mpg = 282.480936 / (L/100km). Because US and UK gallons differ in size, US and UK mpg figures are not interchangeable — the same car gets a higher number in UK mpg.
Frequently asked questions
For US mpg, divide 235.214583 by the mpg value. For example, 30 US mpg equals about 7.84 L/100km.
A UK (imperial) gallon is larger than a US gallon, so the same fuel use gives a higher UK mpg figure. US mpg uses 235.214583 and UK mpg uses 282.480936 as the conversion constant.
For L/100km, lower is more efficient. For mpg and km/L, higher is more efficient — they measure opposite things.
Also known as
TG we-Calculate Editorial Team. (2026). Fuel Economy Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fuel-economy-converter
TG we-Calculate Editorial Team. "Fuel Economy Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/fuel-economy-converter.
TG we-Calculate Editorial Team, "Fuel Economy Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fuel-economy-converter
@misc{wecalculate_fuel_economy_converter, title = {Fuel Economy Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fuel-economy-converter}}, year = {2026}, note = {TG we-Calculate} }
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