Fuel Economy Converter
Convert between L/100km, km/L, MPG (US) and MPG (UK).
Compare fuel economy across regions. Convert between L/100km (consumption) and MPG or km/L (distance per fuel). Note these are inverse measures, so the conversion divides rather than scales.
Formula / method
Examples
29.40
7.84
Two ways to measure thirst
Fuel economy is expressed either as distance per fuel (km/L, or miles per gallon) or as fuel per distance (litres per 100 km). These are inverses, so they move in opposite directions: a bigger MPG or km/L means a more efficient car, but a bigger L/100km means a thirstier one. This tool converts cleanly between L/100km, km/L, US MPG, and UK MPG.
US and UK gallons differ, which trips people up constantly: an imperial (UK) gallon is about 4.546 litres versus 3.785 for the US gallon, so the same car rates roughly 20 percent higher in UK MPG.
Reading the results honestly
Because L/100km is a per-distance measure, small changes at the thirsty end matter more than at the efficient end; dropping from 12 to 10 L/100km saves more fuel over a trip than going from 6 to 5. This is the same reason MPG can be misleading when comparing cars.
Manufacturer figures come from lab cycles and rarely match real driving, so use conversions to compare like with like rather than as a promise of what your tank will deliver. For trip cost estimates, combine the result with distance and a price per litre.
Where it's used
- Comparing a US car's MPG rating against a European L/100km figure
- Converting between US and UK (imperial) MPG, which use different gallons
- Reading a fuel-economy spec given in km/L
- Comparing two cars advertised in different units
- Estimating fuel use for a trip after converting to a familiar unit
Real-world examples
- 8 L/100km converts to about 29.4 US MPG.
- A car rated 30 US MPG uses roughly 7.84 L/100km.
- 40 US MPG is about 48 UK MPG — the same car, because an imperial gallon (~4.546 L) is larger than a US gallon (~3.785 L).
- Dropping from 12 to 10 L/100km saves more fuel per trip than going from 6 to 5 L/100km.
Did you know?
Because MPG measures distance per unit of fuel, it is deceptive: improving a car from 10 to 20 MPG saves far more fuel over the same distance than going from 30 to 40 MPG. This "MPG illusion" is one reason many countries prefer L/100km.
FAQ
Why is mpg ↔ L/100km not a simple multiply?
They measure opposite things: mpg is distance per unit of fuel, L/100km is fuel per distance. So you divide rather than scale linearly.