Fuel Economy Converter
Fixpio’s fuel economy converter restates how thirsty a vehicle is in the unit your country uses — litres per 100 kilometres, kilometres per litre, US miles per gallon or UK miles per gallon — instantly, in your browser. Type a figure, pick your two units, and the answer updates as you type: a European brochure quoting L/100km, a US review in mpg, or a hire-car readout in km/L. One thing catches people out: for litres per 100 km a LOWER number is better, while for mpg and km/L a HIGHER number is better — they measure the same economy from opposite directions.
Convert Fuel Economy
Enter a figure and choose your units — the result appears straight away.
All values are converted via litres per 100 km: km/L = 100 ÷ L/100km; US mpg = 235.214583 ÷ L/100km; UK mpg = 282.480936 ÷ L/100km. A zero value has no reciprocal, so that conversion is not defined.
One converter for brochures, reviews and road trips
The fuel figures people convert most, in the units they actually meet.
Comparing cars fairly
A hybrid advertised at 4.5 L/100km (52.3 US mpg) and a rival at 45 US mpg (5.2 L/100km) are closer than the brochures suggest — and the first one still wins. Converting every candidate to one unit makes the shortlist honest.
Trip costs before you set off
Fuel abroad is priced per litre and distances are posted in kilometres. Turning your car’s mpg into L/100km first makes a foreign fuel budget a quick multiplication instead of a guess.
Hire cars and readouts
Many cars let you switch the dashboard between units, and rental paperwork rarely matches your home setting. Converting the readout tells you whether the car is sipping or drinking.
About this converter
Most visits to a fuel consumption converter start with two numbers that refuse to compare: mpg to litres per 100 km for a review, L/100km to mpg for a brochure, or km/L from a dashboard readout. The maths behind every result on this page is the same — the figure is first expressed in litres per 100 km, then converted into the unit you chose, using the fixed relationships US mpg = 235.214583 ÷ L/100km and UK mpg = 282.480936 ÷ L/100km. That is why 7.5 L/100km — a middling family-car figure — reads as 31.4 US mpg, 37.7 UK mpg or 13.3 km/L.
The two mpg figures differ because the gallons differ: a US gallon is 3.78541 litres while an imperial gallon is 4.54609 litres, so a car travelling the same distance on the same fuel counts more miles per (bigger) gallon in Britain. Litres per 100 km avoids the ambiguity entirely, which is why most of the world uses it — but it runs backwards compared with mpg, measuring fuel used per distance rather than distance per fuel. Whichever pair you choose, the car’s economy does not change; only the way it is described does. Treat converted figures as comparisons, not promises: official test-cycle numbers and real-world driving rarely match exactly.
Frequently asked questions
Straight answers about mpg, litres per 100 km and the two kinds of gallon.
How do I convert mpg to litres per 100 km?
Divide 235.214583 by the US mpg figure. A car rated at 40 US mpg uses 235.214583 ÷ 40 = 5.88 litres per 100 km. For UK mpg the constant is larger — divide 282.480936 instead — because the imperial gallon is bigger. In the converter above, just enter the figure and choose your units; the result updates as you type.
Why is a lower L/100km better, but a higher mpg better?
Because they measure opposite things. Litres per 100 km measures fuel consumed over a fixed distance, so using less fuel gives a smaller number. Miles per gallon measures distance travelled on a fixed amount of fuel, so going further gives a bigger number. Both describe the same economy: 5 L/100km (47.0 US mpg) is thriftier than 8 L/100km (29.4 US mpg), even though one number fell and the other rose.
What is the difference between US mpg and UK mpg?
The mile is the same; the gallon is not. A US gallon is 3.78541 litres and an imperial (UK) gallon is 4.54609 litres — about 20% more fuel. The same car therefore records a higher mpg figure in the UK: 7.5 L/100km is 31.4 US mpg but 37.7 UK mpg. Comparing a British review’s mpg with an American one’s without converting overstates the British car’s economy by roughly a fifth.
What is a good fuel economy figure?
As a rough guide in US mpg: under 25 is thirsty, 30–40 is ordinary family-car territory, and 50 or more is hybrid territory. In litres per 100 km the same bands read about 9.4 or more, 5.9–7.8, and 4.7 or less. These are comparisons, not guarantees — official figures come from standard test cycles, and your own driving, load and weather will move the real number.
How do I convert L/100km to km per litre?
Divide 100 by the L/100km figure: km/L = 100 ÷ L/100km. So 6.5 L/100km is 15.4 km/L, and 5 L/100km is exactly 20 km/L. Kilometres per litre is common on Japanese and Indian readouts and brochures, and like mpg, higher is better.
Why does the converter refuse a value of zero?
Because these units are reciprocals of one another. Zero miles per gallon would mean the car uses an infinite amount of fuel per distance, and zero litres per 100 km would mean it travels infinitely far per gallon — neither can be expressed in the other system. Any real figure above zero converts normally.