Fuel Economy Converter: L/100 km, km/L, mpg
Convert fuel economy between litres per 100 km, kilometres per litre, US mpg and UK (imperial) mpg.
Things to keep in mind:
- This tool does not calculate fuel cost or trip expenses; it only converts consumption units.
- Official figures (WLTP, EPA) reflect test conditions; real consumption depends on driving style, load and weather. US EPA and European WLTP figures are not directly comparable even after converting units.
- LPG and electric vehicle consumption (kWh/100 km) are not covered.
Calculator
Result
Enter the values and press Calculate to see the result here.
About this tool
This tool converts a vehicle’s fuel economy between four common units: L/100 km (Europe, Turkey), km/L (common in Asia and Latin America), US mpg and UK mpg.
Reciprocal relation: L/100 km measures "fuel used per distance", the others "distance per fuel", so the relation between them is inverse, not a simple factor. As consumption falls, km/L and mpg rise.
Formulas:
- km/L = 100 ÷ (L/100 km)
- US mpg = km/L × 3.785411784 ÷ 1.609344 ≈ 235.2146 ÷ (L/100 km)
- UK mpg = km/L × 4.54609 ÷ 1.609344 ≈ 282.4809 ÷ (L/100 km)
The constants are exact definitions: 1 mile = 1.609344 km, 1 US gallon = 231 in³ = 3.785411784 L, 1 imperial gallon = 4.54609 L. Because the imperial gallon is larger, the UK mpg figure for the same car is about 20 % higher than the US figure.
Example: a car using 6 L/100 km does 100 ÷ 6 ≈ 16.6667 km/L, 235.2146 ÷ 6 ≈ 39.2024 US mpg and ≈ 47.0802 UK mpg. 10 L/100 km is exactly 10 km/L.
This tool only converts units; use the fuel cost tools for the cost of a trip.
How to use
- Enter the fuel economy value (greater than 0).
- Select its unit under From unit.
- Select the unit you want the result in under To unit.
- Select Calculate; the value in all four units is listed as well.
Notes
The main result is rounded half-up (HALF_UP) to 6 decimals, the unit equivalents to 4 decimals. Every equivalent is computed directly from the entered value with a single division. The value cannot be 0 (zero consumption or zero range is undefined); the minimum is 0.01.
Frequently asked questions
Divide 100 by the L/100 km value: 8 L/100 km = 100 ÷ 8 = 12.5 km/L. The same formula works the other way: 12.5 km/L = 100 ÷ 12.5 = 8 L/100 km.
For US mpg 235.2146 ÷ 30 ≈ 7.8405 L/100 km; for UK mpg 282.4809 ÷ 30 ≈ 9.4160 L/100 km.
The gallons differ: the US gallon is 3.785411784 L, the imperial gallon 4.54609 L. The same consumption looks about 1.2 times higher in UK mpg.
L/100 km is proportional to the fuel used. Going from 20 to 25 mpg saves more fuel than going from 40 to 50 mpg, which is obvious in L/100 km.
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