Fuel Economy Converter
Convert fuel economy between miles per gallon (US and UK), litres per 100 km and kilometres per litre. Type a value and compare a car across every measure. A free, exact fuel economy converter that runs in your browser.
Put two cars on the same footing when their economy is quoted differently. Convert mpg to L/100km, US mpg to UK mpg, or km/L to any of them, and compare a hire car sticker, a spec sheet or your own measured figure. Enter one value and read it in every measure at once.
- Exact, standard factors
- 100% free
- No sign-up, no app
- Instant as you type
- Works offline after first load
1 mpg in every unit
How to use it
- 1
Enter a figure
Type the economy you have, such as 40 mpg or 6 L/100km.
- 2
Pick the units
Choose the measure you entered, including whether an mpg figure is US or UK.
- 3
Compare measures
See it as US mpg, UK mpg, L/100km and km/L together, and copy what you need.
When it comes in handy
Comparing cars
Put a US mpg figure and a European L/100km figure on the same footing before you compare two cars.
Driving abroad
Make sense of a hire car or fuel sticker that uses the units you are not used to.
Tracking your own use
Convert your measured economy into whichever unit your records or apps expect.
Instant, exact & 100% in your browser
The conversion runs right here in your browser using exact, standard factors. Nothing you type is sent to a server, there is no sign-up and no limit, and once the page has loaded it keeps working even with no connection.
Frequently asked questions
- Why is converting mpg to L/100km not a simple multiply?
- Because they measure opposite things. Miles per gallon is distance per fuel, so higher is better, while litres per 100 km is fuel per distance, so lower is better. Converting one to the other means dividing into a constant rather than multiplying, which is why the relationship is inverse, not linear.
- Is US mpg the same as UK mpg?
- No. They use different gallons: the US gallon is smaller, so the same car shows a lower number in US mpg than in UK mpg. A car rated 40 mpg in the UK is only about 33 mpg in US terms. The converter handles both so you can compare like with like.
- What counts as good fuel economy?
- It depends on the car, but as a rough guide a modern petrol car returning under about 6 L/100km, or above roughly 47 UK mpg, is doing well. Because higher mpg and lower L/100km both mean better economy, converting to one consistent unit makes cars easy to rank.
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