Convert L/100 km and MPG both ways, with US MPG by default and Imperial MPG available for comparison.
Advanced options
Table of contents
How to use our L/100 km to MPG Converter
- Choose Convert to match the number you already have: L/100 km to MPG or MPG to L/100 km.
- Enter Fuel use (L/100 km) or Fuel economy (MPG), using a number greater than 0.
- Pick MPG type carefully: US MPG is common in the United States, while Imperial MPG uses a larger gallon.
- Open Advanced options only if you want to change Decimal places, then click Calculate.
- Sanity-check the Converted value against Other MPG type check; if the two MPG numbers look swapped, change MPG type and calculate again.
Definitions
L/100 km: Liters of fuel used to drive 100 kilometers. Lower values mean less fuel used.
MPG: Miles per gallon, or how many miles a vehicle travels on one gallon. Higher values mean farther travel on one gallon.
US MPG: Miles per US liquid gallon. This is the MPG type usually meant in the United States.
Imperial MPG: Miles per Imperial gallon. An Imperial gallon is larger than a US gallon, so Imperial MPG numbers are higher for the same real fuel use.
Fuel used per 100 miles: Gallons used over a fixed 100-mile distance. It makes fuel use easier to compare because lower is better.
Kilometers per liter: Kilometers traveled on one liter of fuel. Higher values mean farther travel on one liter.
Common mistakes and quick fixes
Mistake: Choosing the wrong MPG type when using Fuel economy (MPG).
Fix: Set MPG type to US MPG for United States ratings or Imperial MPG for UK-style ratings before reading Converted value.
Mistake: Entering 0 or a blank value for Fuel use (L/100 km).
Fix: Enter a positive number greater than 0, because the conversion divides by Fuel use (L/100 km).
Mistake: Reading a higher Fuel use (L/100 km) as better fuel economy.
Fix: Remember that lower Fuel use (L/100 km) is better, while higher Fuel economy (MPG) and Kilometers per liter are better.
Mistake: Treating Other MPG type check as the main answer without checking the selected MPG type.
Fix: Use Converted value as the main answer and use Other MPG type check only to spot a US MPG versus Imperial MPG mix-up.
Mistake: Assuming Decimal places changes the actual conversion math.
Fix: Decimal places only changes how many digits are shown; the Rounding note reminds you that the full factor is used internally.
Limitations & Key Assumptions / Boundary Conditions
- The calculator accepts only positive fuel-use or fuel-economy values. Blank, zero, negative, infinite, and non-numeric entries are errors.
- US MPG and Imperial MPG are not interchangeable. The selected MPG type controls the main conversion and the gallon unit for Fuel used per 100 miles.
- Decimal places affects display only. Internal calculations use the full conversion factors before rounding the results.
- Very small positive inputs can create very large outputs. The math is still valid if the input is finite, but the value may not match a realistic vehicle.
- The converter does not include driving style, weather, fuel blend, odometer error, or test-cycle differences. It only converts units.
Methodology
Core conversion
The calculator uses exact unit factors for kilometers per mile and the US liquid gallon where applicable [3]. It also keeps US MPG and Imperial MPG separate because the gallons are different sizes.
factor_us = (100 / 1.609344) * 3.785411784 = 235.214583...
factor_imperial = (100 / 1.609344) * 4.54609 = 282.480936...
When the input is Fuel use (L/100 km), the calculator divides the selected factor by that value.
mpg = factor / L100
When the input is Fuel economy (MPG), the calculator divides the selected factor by the MPG value.
L100 = factor / mpg
Extra results
Other MPG type check repeats the same conversion with the other gallon type, so a US MPG and Imperial MPG mix-up is easier to notice. Fuel used per 100 miles follows the EPA-style idea that gallons over a fixed distance can be easier to compare than MPG alone [2].
gallons_per_100_miles = 100 / mpg
km_per_liter = 100 / L100
Mini-example
For 7.5 L/100 km with MPG type set to US MPG, the main result is calculated as follows.
US MPG = 235.214583 / 7.5 = 31.361944...
With 1 decimal place, Converted value shows 31.4 US MPG. The same 7.5 L/100 km is 37.7 Imperial MPG, Fuel used per 100 miles is about 3.2 US gallons per 100 miles, and Kilometers per liter is 13.3 km/L.