Fuel Efficiency Converter

Convert between miles per gallon (mpg), liters per 100km (L/100km), and kilometers per liter (km/L).

Fuel Efficiency Converter tool

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Example

Input: 30 miles per gallon (US mpg) to liters per 100 km (L/100km)

Result: 7.8405 L/100km

L/100km = 235.215 / mpg, so 235.215 / 30 = 7.8405 L/100km.

US mpg to L/100km and km/L

US mpgL/100kmkm/L
1023.52154.2514
1515.6816.3772
2011.76078.5029
259.408610.6286
307.840512.7543
356.720414.88
405.880417.0057
504.704321.2572

Values from this converter, rounded to 4 decimal places.

  1. Select the fuel efficiency unit you want to convert from (mpg, L/100km, or km/L).
  2. Enter your vehicle fuel efficiency value in the input field.
  3. See the equivalent fuel economy in the other two standards calculated instantly.
  4. Compare international vehicle specifications by converting between regional fuel economy formats.
  5. Copy the converted fuel efficiency value to use in vehicle comparisons or trip planning.

Why mpg and L/100km Move in Opposite Ways

To convert US mpg to liters per 100 km, divide 235.215 by the mpg figure, so 30 mpg is 7.84 L/100km. The same division works in reverse. This converter handles miles per US gallon, liters per 100 km and kilometers per liter.

These units measure two different things. Miles per gallon and km per liter tell you how far you go on a set amount of fuel. Liters per 100 km tells you how much fuel a set distance takes. That is why the numbers move in opposite directions. A thirstier car has a lower mpg but a higher L/100km.

This flip hides a useful fact. Moving from 10 to 20 mpg saves 11.76 liters every 100 km. Moving from 30 to 40 mpg saves just 1.96 liters. So upgrading the least efficient vehicle saves far more fuel than improving an already frugal one. L/100km shows this plainly, which is why many countries use it.

Check which gallon you have before you convert. This tool uses the US gallon of 3.785 liters. A UK mpg figure is based on the larger 4.546 liter gallon. It reads about 20 percent higher for the same car, so 36 UK mpg is about 30 US mpg. To switch gallons and liters for a fill-up, use the Volume Converter. Electric cars are rated in different units, such as kWh per 100 km, which this tool does not cover.

Formula / How It Works

mpg (US) to L/100km: divide 235.215 by mpg | mpg to km/L: multiply mpg by 0.425144 | L/100km to km/L: divide 100 by L/100km

Sources

Frequently Asked Questions

Divide 235.215 by the US mpg figure. So 25 mpg is 9.41 L/100km and 30 mpg is 7.84 L/100km. The numbers move in opposite directions: a higher mpg means a lower L/100km. That is because mpg measures distance per fuel, while L/100km measures fuel per distance.
Use the same number: divide 235.215 by the L/100km figure. A car that uses 6 L/100km gets 39.2 US mpg, and one that uses 8 L/100km gets 29.4 mpg. Because the formula works both ways, you can also just pick L/100km as the From unit in the converter.
A UK gallon is about 20 percent bigger than a US gallon, so the same car gets a higher UK mpg figure. Multiply US mpg by 1.201 to get UK mpg: 30 US mpg is about 36 UK mpg. This converter uses US gallons, so divide a UK figure by 1.201 before you enter it.
Kilometers per liter is how far a car goes on one liter of fuel. It is used in countries such as Japan and India. To get it from L/100km, divide 100 by the figure: 8 L/100km is 12.5 km/L. To get it from US mpg, multiply by 0.425144, so 30 mpg is 12.75 km/L.
It tells you directly how much fuel a trip will take. Going from 10 to 20 mpg saves 11.76 liters every 100 km. Going from 30 to 40 mpg saves only 1.96 liters. The mpg gap looks the same, but the fuel saved is very different, and L/100km makes that plain.

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