Converters
Fuel Economy Converter
Convert km/L, L/100 km, US mpg, and UK mpg.
About This Tool
Compare vehicle fuel economy figures that use different measurement systems. This converter handles kilometers per liter (km/L), liters per 100 kilometers (L/100 km), miles per US gallon, and miles per imperial gallon. It keeps US and UK gallons separate and correctly handles L/100 km, where a lower number means less fuel is used for the same distance.
How To Use It
- Enter a fuel economy value greater than zero.
- Choose the unit used by the original vehicle specification or measurement.
- Choose the target unit, making sure to select US mpg or imperial mpg as appropriate.
- Review the converted result and comparison table; use Swap when you want to reverse the selected units.
Examples
20 km/L to L/100 km
A vehicle achieving 20 km/L uses 5 L/100 km because the two metric measures have an inverse relationship: 100 ÷ 20 = 5.
30 US mpg to km/L
30 miles per US gallon is about 12.7543 km/L using exactly 1 mile = 1.609344 km and 1 US gallon = 3.785411784 liters.
40 imperial mpg to US mpg
40 imperial mpg is about 33.3067 US mpg. The numeric mpg value changes because an imperial gallon is larger than a US gallon.
8 L/100 km to km/L
8 L/100 km equals 12.5 km/L. Lower L/100 km indicates better fuel economy, while higher km/L or mpg indicates better fuel economy.
Useful Notes
Why L/100 km works differently
Kilometers per liter and mpg describe distance traveled per unit of fuel, so larger values indicate better fuel economy. L/100 km describes fuel consumed for a fixed distance, so smaller values indicate better fuel economy. Converting between km/L and L/100 km uses the reciprocal formula: L/100 km = 100 ÷ km/L.
US mpg and imperial mpg are different
A US liquid gallon is exactly 3.785411784 liters. An imperial gallon is exactly 4.54609 liters. Because the gallon sizes differ, an mpg figure is ambiguous unless the gallon system is known. This tool labels them separately rather than assuming they are interchangeable.
Conversion constants
The converter uses exactly 1 international mile = 1.609344 kilometers, 1 US liquid gallon = 3.785411784 liters, and 1 imperial gallon = 4.54609 liters. Values are normalized through kilometers per liter before being displayed in the selected unit.
Rated economy versus real driving
This tool converts an existing fuel-economy figure; it does not predict a vehicle's actual consumption. Real-world results can vary with speed, traffic, weather, terrain, load, tire pressure, driving style, vehicle condition, and test methodology.
FAQ
Is US mpg the same as UK mpg?
No. US mpg uses the US liquid gallon, while UK or imperial mpg uses the larger imperial gallon. Always choose the gallon system used by the source figure.
Is a lower L/100 km better?
Yes. L/100 km measures fuel consumed over 100 kilometers, so a lower value means less fuel is required for that distance.
Is a higher mpg or km/L better?
Yes. Both mpg and km/L measure distance traveled per amount of fuel, so larger values represent greater fuel economy.
Why can't I convert zero L/100 km?
These fuel-economy units are related by reciprocal formulas. A zero consumption value would require division by zero and does not produce a finite equivalent in distance-per-fuel units, so this converter requires values greater than zero.
Does this calculate fuel cost?
No. It converts fuel-economy units only. Fuel cost also depends on distance traveled and the current price of fuel.
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