A fuel economy converter changes a consumption figure among four named units: US miles per gallon, Imperial miles per gallon, litres per 100 kilometres, and kilometres per litre. This fuel economy converter does not use one multiply for every pair. Litres per 100 kilometres and kilometres per litre are reciprocals. Miles per gallon also runs in the opposite direction from litres per 100 kilometres: a larger mpg is a smaller L/100 km.
The page normalizes every input to litres per kilometre, then converts that rate into the unit you asked for. For L/100 km, litres per kilometre is the value divided by 100. For km/L, litres per kilometre is 1 divided by the value. For US mpg, litres per kilometre is 3.785411784 divided by the value times 1.609344. For Imperial mpg, the numerator is 4.54609 instead of 3.785411784. Those three constants are exact on this page: the international mile is 1.609344 km, the US gallon is 3.785411784 L, and the Imperial gallon is 4.54609 L.
The two gallons are the reason an unlabeled “mpg” field would be wrong. A US gallon and an Imperial gallon are not the same volume, so 30 US mpg is not 30 Imperial mpg. The labels on this page say US or Imperial. Volume Converter already states the same two litre definitions for the gallons. This page is the consumption conversion. It does not convert a tank volume by itself, and it does not convert a road speed.
Zero and negative values are rejected. A reciprocal of zero is not a fuel economy. There is no fuel price, no trip distance, and no “good mileage” judgment. Type the figure you already have and name the unit printed beside it.
Empty input and non-numeric input fail. A magnitude above 1e15 is refused. Commas used as thousands separators are removed before the conversion, matching the other unit converters. Enter on the field or either list runs the conversion. The result shows the number and the destination unit name, including US or Imperial when the destination is miles per gallon.
30 US mpg is 7.840486111111 L/100 km, 12.754311222908 km/L, and 36.028497765146 Imperial mpg. 8 L/100 km is 29.401822916667 US mpg, 35.310117041478 Imperial mpg, and 12.5 km/L. The display uses at most 12 digits after the decimal and then removes trailing zeros, so 12.5 stays 12.5. Converting a value into the same unit returns that value for these inputs.
30 US mpg = 7.840486111111 L/100 km
30 US mpg = 12.754311222908 km/L
30 US mpg = 36.028497765146 Imperial mpg
8 L/100 km = 29.401822916667 US mpg
8 L/100 km = 12.5 km/LPeople compare a US window sticker in mpg with a European figure in L/100 km and treat the two numbers as if a bigger number always means the same thing. It does not. Use the direction in Example: 30 US mpg is about 7.84 L/100 km, not 30 L/100 km. An Imperial gallon is larger than a US gallon, so the same car prints a higher mpg in Imperial units than in US units. That gap is the gallon, not a change in the car.
Kilometres per litre and litres per 100 kilometres describe the same trip in opposite directions. 8 L/100 km is 12.5 km/L because 100/8 is 12.5. Dividing when the page expects a multiply, or the other way around, is the mistake the litres-per-kilometre step is there to prevent. If you only need the size of a gallon in litres, the constants are printed above. If you need a currency amount for a journey, this page will not invent a price.
Scientific notation is accepted when the number is finite, greater than zero, and inside the magnitude limit. A blank field remains an error after Swap units. Keyboard users can press Enter from the value or either unit list.
US mpg uses the US gallon of 3.785411784 L. Imperial mpg uses the Imperial gallon of 4.54609 L. The mile is 1.609344 km. The value must be greater than zero. This page does not calculate a fuel cost.
No. US mpg uses a gallon of 3.785411784 L. Imperial mpg uses a gallon of 4.54609 L.
Litres per 100 km and miles per gallon run in opposite directions. The page converts through litres per kilometre.
No. There is no price and no trip distance. It only converts the economy figure.
Kilometres per litre and miles per gallon are undefined at zero because the conversion divides by the value.