Unit Converters
Fuel Efficiency Converter
Fuel Efficiency: fuel Efficiency Converter converts between fuel-economy units (mpg, km/l and L/100 km) using their fixed reciprocal relationships. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
Enter your efficiency value plus the source and target units and Fuel Efficiency Converter works out the converted fuel economy in the unit you choose with fixed, standard conversion ratios — fast, free and private, with no sign-up or uploads.
About this calculator
It matters whenever the same quantity is expressed in two systems and a wrong factor silently breaks the answer. The governing relationship: Fuel Efficiency Converter converts between fuel-economy units (mpg, km/l and L/100 km) using their fixed reciprocal relationships. See it on real numbers: Convert 40 mpg (US) to L/100km: 235.215 ÷ 40 = 5.88 L/100km . The calculator above applies the same steps to whatever you enter — computed locally, nothing sent anywhere.
How to use
- Enter the efficiency value.
- Choose the From unit.
- Choose the To unit.
- Press Calculate to convert the efficiency.
Why use Fuel Efficiency Converter
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard conversion factors where applicable. Check critical engineering or measurement results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it for cross-checking a calculation
Use it for coursework and homework
Use it when reading a spec sheet
Fuel Efficiency in design and manufacturing
Fuel Efficiency in trade and workshop work
Use it when a manual uses different units
Technical notes
Fuel Efficiency Converter converts between fuel-economy units (mpg, km/l and L/100 km) using their fixed reciprocal relationships.
Conversions use standard reference factors; for trade or engineering tolerances keep more decimal places than the display shows.
Results are rounded for display; the underlying calculation keeps full precision.
FAQ
Which efficiency units are supported?
mpg (US), mpg (UK), km/L, and L/100km.
Is 20 km/L the same as 5 L/100km?
Yes. L/100km is the inverse measure, so a higher km/L means a lower L/100km.
Are US and UK gallons different?
Yes. A UK gallon is larger, so mpg (UK) and mpg (US) values are not the same.
Does the Fuel Efficiency Converter send my data to a server?
No. The Fuel Efficiency Converter runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
Convert 40 mpg (US) to L/100km: 235.215 ÷ 40 = 5.88 L/100km.