KM/L to MPG Converter

Convert km/L to US or Imperial MPG, or use trip distance and liters to find the same answers.

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How to use
Common mistakes
Definitions
Methodology
Limitations & assumptions
Sources

How to use our KM/L to MPG Converter

Choose What do you want to enter?: I know the km/L for a ready fuel economy rating, or Use distance and liters for trip data.
If you choose I know the km/L, enter Fuel economy (km/L). If you choose Use distance and liters, enter Distance driven (km) and Fuel used (liters) from the same trip.
Pick MPG gallon type: US gallon for US-style MPG, or Imperial gallon for UK-style MPG.
Select Calculate and read MPG using your selected gallon type first, then compare the other gallon type, L/100 km, and gal/100 mi.
Sanity-check the result: higher MPG and higher km/L mean better fuel economy, while lower Fuel used per 100 km and lower Fuel used per 100 miles mean less fuel used.

Example inputs for KM/L to MPG Converter

Definitions

km/L: Kilometers per liter. It means how many kilometers a vehicle travels on 1 liter of fuel.

MPG: Miles per gallon. It means how many miles a vehicle travels on 1 gallon of fuel.

US gallon: A liquid gallon equal to 3.785411784 liters, used for US MPG conversions [1].

Imperial gallon: A gallon equal to 4.54609 liters, used for Imperial or UK MPG conversions [1].

L/100 km: Liters per 100 kilometers. It measures fuel used for a fixed distance, so lower is better.

gal/100 mi: Gallons per 100 miles. The EPA fuel economy label uses MPG and gallons per 100 miles to describe fuel economy and fuel use [2].

MPG by gallon type

Imperial MPG is higher because the Imperial gallon is larger.

Common mistakes and quick fixes

Mistake: Mixing up MPG gallon type and reading the answer as just plain MPG.
Fix: Choose US gallon or Imperial gallon before using MPG using your selected gallon type.

Mistake: Entering miles in Distance driven (km).
Fix: Convert the trip distance to kilometers first, then enter it in Distance driven (km).

Mistake: Using a fuel amount from a different fill-up than the distance in Distance driven (km).
Fix: Fuel used (liters) must match the same trip or tank as Distance driven (km).

Mistake: Typing 0, a blank value, or a negative number in Fuel economy (km/L).
Fix: Enter a positive Fuel economy (km/L), such as 12.

Mistake: Comparing Fuel used per 100 km as if bigger is better.
Fix: For Fuel used per 100 km and Fuel used per 100 miles, lower means less fuel used.

Limitations & Key Assumptions / Boundary Conditions

The converter assumes the entered km/L, Distance driven (km), and Fuel used (liters) are already measured correctly.
Trip mode uses simple average fuel economy: Distance driven (km) divided by Fuel used (liters). It does not adjust for traffic, weather, tire pressure, fuel blend, or driving style.
US MPG and Imperial MPG are not interchangeable because the gallon sizes are different.
Very small positive km/L values can create very large Fuel used per 100 km values; that usually means the input is not a normal vehicle fuel economy rating.
Results are rounded for display, so hand calculations may differ by a tiny amount.
The tool does not estimate fuel cost, carbon emissions, city MPG, highway MPG, or official test-cycle ratings.

Methodology

How the converter chooses km/L

The first step is to get one km/L value. If What do you want to enter? is I know the km/L, the converter uses Fuel economy (km/L). If it is Use distance and liters, it divides Distance driven (km) by Fuel used (liters).

km_l = fuel_efficiency_kml

km_l = distance_km / fuel_used_liters

Unit conversions

The conversion uses 1 mile = 1.609344 km, 1 US liquid gallon = 3.785411784 liters, and 1 Imperial gallon = 4.54609 liters [1].

mpg_us = km_l x (3.785411784 / 1.609344)

mpg_imperial = km_l x (4.54609 / 1.609344)

If MPG gallon type is US gallon, MPG using your selected gallon type is the US MPG value and MPG using the other gallon type is the Imperial MPG value. If MPG gallon type is Imperial gallon, those two values switch places.

Fuel used over fixed distances

L/100 km flips km/L into fuel used for a fixed 100 km distance. Gallons per 100 miles does the same for the selected MPG answer.

liters_per_100_km = 100 / km_l

selected_gallons_per_100_miles = 100 / selected_mpg

Mini example

For Fuel economy (km/L) = 12 and MPG gallon type = US gallon, US MPG is 12 x 2.352145833333333 = 28.22575 mpg. Imperial MPG is 12 x 2.824809363318222 = 33.8977123598 mpg. Fuel used per 100 km is 100 / 12 = 8.3333333333 L/100 km, and Fuel used per 100 miles is 100 / 28.22575 = 3.5428642286 gal/100 mi.

Validation and rounding

The calculator strips commas and spaces before reading numbers. It requires positive values for Fuel economy (km/L), Distance driven (km), and Fuel used (liters), depending on the selected entry mode. Displayed results are rounded to readable decimals, while the formulas use the constants shown above.