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MPG to L/100km Calculator

Convert MPG to L/100km and km/L.

Result

7.84 L/100km
12.75 km/L

How it is calculated

The tool converts US miles per gallon into the metric measures of fuel use. L/100 km = 235.2146 / MPG and km/L = MPG × 0.4251437. The factors come from 1 US gallon = 3.785 L and 1 mile = 1.609 km. Note that L/100 km measures fuel used per distance, so a lower number is better, while MPG and km/L measure distance per fuel, where a higher number is better. The conversion uses the US gallon; UK (imperial) gallons are about 20% larger, so UK MPG figures give different values. MPG must be above zero.

Worked example

A car does 30 US MPG. L/100 km = 235.2146 / 30 = 7.84 L/100km. Distance per litre: 30 × 0.4251437 = 12.75 km/L. As a check, 100 km / 12.75 km per litre is about 7.84 litres. A car at 60 MPG would use half as much fuel, 3.92 L/100 km.

Try this example →

Common mistakes

  • Entering a UK (imperial) MPG figure, which is based on a larger gallon; US MPG is the input here.
  • Assuming L/100 km and MPG move in the same direction; one goes up as the other goes down.
  • Averaging MPG values of two trips directly; average the L/100 km instead.
  • Believing that going from 10 to 20 MPG saves as much fuel as going from 30 to 40 MPG; the first saves much more.
  • Entering 0 or leaving the field empty, which returns no result.

About this calculator

This calculator converts between fuel-economy scales using the identity L/100km = 235.214583 / MPG(US), which follows from the different units each region uses to express the same physical quantity: the US measures distance travelled per unit of fuel, while Europe measures fuel burned per fixed distance. Because one is a rate and the other is a rate's reciprocal, the two scales are non-linear relative to each other — a jump from 40 to 50 MPG saves far less fuel than a jump from 15 to 20 MPG, even though the MPG gap is twice as large.

Car buyers comparing a US-spec window sticker against a European brochure, importers registering a vehicle in a new market, and automotive journalists writing about efficiency across regions all rely on this conversion, since manufacturers rarely publish both figures for the same market. It also matters for road-trip planning and fleet cost estimates when mixing sources that quote consumption differently.

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Comments (1)

  • Editorial team

    Miles per gallon and litres per 100 km are not proportional, which hides where savings are. Going from 20 to 30 MPG cuts consumption from 11.76 to 7.84 litres per 100 km, a saving of 3.92. Going from 30 to 40 MPG, a bigger-looking jump in the other scale, only saves a further 1.96. The tool assumes US gallons. Which MPG figure are you comparing, US or UK?

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