Softonic

Fuel Consumption Converter

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Car specs use three different scales for fuel efficiency: MPG in the US and UK (but with different gallons), L/100 km across most of Europe, and km/L in parts of Asia and Latin America. This converter translates any value into all three so you can compare a 32 MPG SUV with a 7.8 L/100 km hatchback without pulling out a napkin.

How to convert fuel economy

  1. 1

    Enter the value you know

    MPG (US), MPG (UK), L/100 km or km/L.

  2. 2

    Pick the source unit

    Selecting the wrong gallon gives a 20% error: MPG UK ≠ MPG US.

  3. 3

    Read the converted values

    The result appears in the unit you chose; pick another target unit to see any other scale.

Formulas

From → To Formula
MPG (US) → L/100 km L/100 km = 235.2145 / MPG
MPG (UK) → L/100 km L/100 km = 282.4810 / MPG
L/100 km → MPG (US) MPG = 235.2145 / (L/100 km)
L/100 km → km/L km/L = 100 / (L/100 km)

The constants come from 1 US gallon = 3.78541 L, 1 UK gallon = 4.54609 L and 1 mile = 1.60934 km.

Why L/100 km is the inverse of MPG

MPG measures distance per fuel while L/100 km measures fuel per distance. Doubling MPG halves L/100 km, not the other way around, so comparing improvements across scales is tricky.

MPG (US) L/100 km km/L
20 11.76 8.5
30 7.84 12.8
40 5.88 17.0
50 4.70 21.3
60 3.92 25.5

Watch the gallon

A car rated 40 MPG (UK) is 33.3 MPG (US), the sticker looks worse simply because US gallons are smaller. Always check whether a figure comes from the manufacturer’s home market or the WLTP/EPA cycle.

Frequently Asked Questions

Because consumption is a hyperbolic function of MPG. 15 → 20 MPG drops L/100 km from 15.7 to 11.8 (~4 L saved per 100 km), while 35 → 40 only saves ~1 L. This is the “MPG illusion”.

They are mathematically equivalent, but L/100 km is easier to budget with: double the distance, double the fuel. MPG hides that relationship.

WLTP is closer to reality than the old NEDC cycle but still tends to understate real-world consumption by 10–20% depending on driving style and climate.

No. The value is sent to our server to run the conversion and may appear in the page link during the guided steps; the value itself is not stored.

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