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Fuel economy converter (mpg, L/100 km, km/L)

Miles per gallon (US and UK), litres per 100 km and kilometres per litre, converted with the correct reciprocal formulas.

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Frommiles per US gallon (mpg (US))
1
Tolitres per 100 km (L/100 km)
235.2145833
DecimalsAuto (up to 10 significant digits)

Formula: L/100 km = 235.214583333 ÷ mpg (US)

1 mpg (US) = 235.2145833 L/100 km

Common values: miles per US gallon to litres per 100 km

mpg (US)L/100 km
10 mpg (US)23.52145833 L/100 km
15 mpg (US)15.68097222 L/100 km
20 mpg (US)11.76072917 L/100 km
25 mpg (US)9.408583333 L/100 km
30 mpg (US)7.840486111 L/100 km
35 mpg (US)6.720416667 L/100 km
40 mpg (US)5.880364583 L/100 km
45 mpg (US)5.226990741 L/100 km
50 mpg (US)4.704291667 L/100 km
60 mpg (US)3.920243056 L/100 km

How it works

Fuel economy is quoted two ways. Distance per fuel (miles per gallon in the US and UK, kilometres per litre in India, Japan and much of Latin America) grows as a car gets more efficient. Fuel per distance (litres per 100 km, used in Europe, Australia, China and the Gulf) shrinks. Converting between them is a reciprocal, not a multiplication, which is why the formula line shows a division.

The constants follow from the exact mile (1.609344 km) and gallons: L/100 km = 235.2146 ÷ mpg (US) and L/100 km = 282.4809 ÷ mpg (UK); km/L = 100 ÷ L/100 km. A car rated 30 mpg in the US uses 7.84 L/100 km; the same car is about 36 mpg in UK units, because the imperial gallon is 20% larger. Zero cannot be inverted, so 0 L/100 km or 0 mpg shows a dash instead of infinity.

Because of the reciprocal, improvements look different on each scale: going from 10 to 20 mpg saves far more fuel than going from 40 to 50 mpg, which is obvious in L/100 km (23.5 → 11.8 versus 5.9 → 4.7).

Common fuel economy conversions

Litres per 100 km measures fuel used (lower is better) while miles per gallon and km per litre measure distance travelled (higher is better), so the conversion is a reciprocal, not a single factor. US and UK mpg use different gallons.

  • 1 L/100 km = 235.2145833 mpg (US) (mpg (US) = 235.214583333 ÷ L/100 km)
  • 1 mpg (US) = 235.2145833 L/100 km (L/100 km = 235.214583333 ÷ mpg (US))
  • 1 mpg (UK) = 282.4809363 L/100 km (L/100 km = 282.480936332 ÷ mpg (UK))
  • 1 km/L = 100 L/100 km (L/100 km = 100 ÷ km/L)
  • 1 mpg (US) = 1.200949926 mpg (UK) (mpg (UK) = mpg (US) × 1.2009499255)
  • 1 km/L = 2.352145833 mpg (US) (mpg (US) = km/L × 2.35214583333)

Every fuel economy unit in this converter

The size of each unit in kilometres per litres (km/L), the base unit the converter uses internally. Values are exact where the unit has an exact definition.

UnitIn km/L
kilometres per litre (km/L)1 km/L
litres per 100 km (L/100 km)100 ÷ value km/L
miles per US gallon (mpg (US))0.4251437074 km/L
miles per imperial gallon (mpg (UK))0.3540061899 km/L

How to use it

  1. Pick the figure you have: US mpg, UK mpg, L/100 km or km/L.
  2. Pick the scale you want and type the value in either box.
  3. Check the table for common ratings.

Frequently asked questions

How do I convert mpg to L/100 km?

Divide 235.215 by US mpg (or 282.481 by UK mpg). 25 mpg (US) = 9.41 L/100 km.

Why is UK mpg higher than US mpg for the same car?

An imperial gallon is 4.546 L and a US gallon 3.785 L, so a car travels about 20% farther on a UK gallon. Multiply US mpg by 1.201 to get UK mpg.

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

Divide 100 by the km/L figure. 15 km/L = 6.67 L/100 km.

What happens if I enter 0?

Zero has no reciprocal (it would mean infinite fuel economy or consumption), so the converter shows a dash and a note instead of a meaningless number.

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