Fuel Economy Converter
Kilometres per litre, miles per gallon, and litres per 100 kilometres describe fuel efficiency in genuinely different directions — two of them measure 'distance per fuel' while the third measures 'fuel per distance', which is exactly why higher is better for two of them but lower is better for the third.
Inputs
Result
42.339 MPG (US)
How the fuel economy converter works
km/l and MPG (US) both increase with better efficiency: MPG (US) = km/l ÷ 0.425144.
L/100km decreases with better efficiency, since it directly measures fuel consumed per fixed distance: L/100km = 100 ÷ km/l.
Worked example: 18 km/l converted to MPG (US) and L/100km
- MPG (US) = 18 ÷ 0.425144 ≈ 42.34 mpg.
- L/100km = 100 ÷ 18 ≈ 5.56 L/100km.
Common mistakes to avoid
Assuming a higher L/100km figure means better fuel economy, following the pattern of the other two units
L/100km is inverted relative to km/l and MPG — a lower L/100km figure means better efficiency (less fuel needed per 100km), the opposite direction from km/l and MPG where a higher number is better.
Comparing US MPG directly against a UK-quoted MPG figure
As with the Volume Converter's gallon distinction, a US MPG and a UK (imperial) MPG use different-sized gallons, making the same numeric MPG figure represent meaningfully different real fuel efficiency between the two conventions.
Frequently asked questions
Why does L/100km use a fixed-distance approach instead of fixed-fuel like the other units?
It's simply a different, and arguably more intuitive, way of framing the same underlying efficiency — 'how much fuel does this specific trip length require' rather than 'how far does this specific amount of fuel take me', and it's the standard convention in much of Europe and elsewhere.
Is a US MPG figure the same as a UK MPG figure for the identical car?
No — since the US gallon and UK gallon differ in size, the same real fuel efficiency produces different MPG numbers depending on which gallon convention is used, making direct comparison without conversion misleading.
Why does the L/100km-to-km/l conversion use a reciprocal (100 ÷ value) rather than a simple multiplication?
Because the two units measure the relationship in opposite directions (distance-per-fuel versus fuel-per-distance), converting between them requires inverting the relationship (dividing into a constant) rather than the straightforward proportional scaling used for most other unit conversions.
How is this related to the Fuel Cost Calculator?
That tool uses a km/l-style efficiency figure directly to calculate a trip's total fuel cost; this converter simply translates that efficiency figure between different fuel-economy unit conventions, which is a useful preliminary step if the original efficiency figure is quoted in an unfamiliar unit.
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