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Fuel Economy Converter

Convert mpg to L/100 km, UK mpg to US mpg, or km/L to L/100 km, both ways, with the exact formula.

Convert fuel economy

 
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All fuel economy units

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Fuel Economy Converter by Freebiefy, free online tools

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The fuel economy units

  • Miles per gallon, US (mpg): miles driven on one US gallon of 3.785411784 liters. Higher is better.
  • Miles per gallon, UK: miles driven on one imperial gallon of 4.54609 liters. The same car shows a higher number than in US mpg.
  • Liters per 100 kilometers (L/100 km): fuel used to drive 100 km. Lower is better.
  • Kilometers per liter (km/L): kilometers driven on one liter. Higher is better.

The formula

mpg and km/L count distance per fuel, while L/100 km counts fuel per distance. That makes them inverses, so there is no single factor to multiply by. With a mile of exactly 1.609344 km:

  • L/100 km = 235.215 ÷ mpg (US) and mpg (US) = 235.215 ÷ L/100 km
  • L/100 km = 282.481 ÷ mpg (UK)
  • L/100 km = 100 ÷ km/L
  • km/L = mpg (US) × 0.425144

Because of the inverse, steps in mpg do not save the same fuel everywhere. Going from 10 to 20 mpg cuts the use from 23.5 to 11.8 L/100 km, while going from 40 to 50 mpg only cuts it from 5.9 to 4.7 L/100 km.

US mpg to L/100 km

Miles per gallon (US) (mpg)Liters per 100 kilometers (L/100 km)
1023.52
1515.68
2011.76
259.409
307.84
356.72
405.88
455.227
504.704
603.92

How to use it

  1. 1Pick the unit you have on the left and the one you want on the right. US mpg to L/100 km is set up when the page opens.
  2. 2Type the value. Either side accepts input, and swap turns the conversion around.
  3. 3Read the result, the formula and the same figure in the other units. Copy the number or a link.

Frequently asked questions

How do I convert mpg to L/100 km?

Divide 235.215 by the mpg figure. 30 mpg is 235.215 ÷ 30, about 7.84 L/100 km. The same formula works the other way: 235.215 ÷ L/100 km gives US mpg.

Why does the conversion use division instead of a factor?

Miles per gallon measures distance per fuel, and L/100 km measures fuel per distance. One is the inverse of the other, so a higher mpg means a lower L/100 km.

What is the difference between US and UK mpg?

The UK gallon is 4.54609 liters and the US gallon 3.785411784 liters. A car that does 30 US mpg does about 36 UK mpg, because the UK gallon is bigger.

How do I convert km/L to L/100 km?

Divide 100 by the km/L figure. 20 km/L is 5 L/100 km.