Free Fuel Economy Converter – MPG, km/L & L/100km

What a Fuel Economy Converter Does and How It Works

A fuel economy converter translates how far a vehicle travels on its fuel between the systems used around the world: miles per gallon in both US and UK forms, kilometres per litre, and litres per 100 kilometres. Enter a figure in one and the others follow. This is genuinely harder than most conversions because the units do not all point the same way. Miles per gallon and kilometres per litre measure distance covered per unit of fuel, so a higher number is better, while litres per 100 kilometres measures fuel burned over a fixed distance, so a lower number is better. Anyone buying, importing, or comparing cars across markets runs into this mismatch, and getting it wrong makes an efficient car look thirsty or the reverse. The method has to respect that inverse relationship. You cannot turn miles per gallon into litres per 100 kilometres by multiplying by a single factor, because one is distance-over-fuel and the other is fuel-over-distance; the two are reciprocals. The converter first turns your input into a common internal measure, then takes the reciprocal where needed. The useful anchors are that 1 US gallon is 3.78541 litres and 1 imperial (UK) gallon is 4.54609 litres, and that litres per 100 kilometres equals 235.215 divided by US miles per gallon, or 282.481 divided by UK miles per gallon. Kilometres per litre and litres per 100 kilometres are linked by km/L = 100 divided by the L/100km figure. Here is a concrete example. A car rated at 40 US miles per gallon converts to litres per 100 kilometres as 235.215 ÷ 40, which is about 5.88 L/100km, a fairly economical figure. The same 40 in km/L terms is 40 × 1.60934 ÷ 3.78541, roughly 17 km/L. Going the other way, a European car listed at 6 L/100km is 235.215 ÷ 6, about 39.2 US mpg. Enter 40 in the US mpg box and the tool shows about 5.88 L/100km and 17 km/L together, so you can judge the car in whichever unit you understand best. The practical uses are specific. A buyer comparing a US-market car at 35 mpg with a European one at 7 L/100km converts both to one unit and finds the European car is slightly thirstier. An importer works out a vehicle's economy in the local standard before registration. A driver logs their own mileage in km/L and converts to L/100km to compare with the manufacturer's quoted figure. Someone reading a UK review in imperial mpg converts to US mpg to compare with an American review, avoiding the gallon-size trap. A delivery firm costing a route budgets fuel from a van rated at 8 L/100km, which is about 29.4 US mpg, and a rideshare driver tracking 14 km/L reads it as 7.14 L/100km to compare with the sticker. Fleet managers setting efficiency targets, and anyone deciding whether a 5 L/100km hybrid justifies its premium over a 7 L/100km petrol car, work through the same conversion. Seeing several units at once makes fair comparison easy. A couple of cautions really matter. The gallon is the big one: a UK gallon is about 20 percent larger than a US gallon, so the same car shows a higher mpg in UK figures, and comparing a UK mpg directly with a US mpg overstates the difference. Always convert to a common gallon first. The second is the higher-is-better versus lower-is-better flip, so remember that a small L/100km number is good while a small mpg number is poor. Beginners also assume the difference between 20 and 25 mpg is the same as between 40 and 45, but savings shrink as economy rises, and the first five matter far more per mile than the second five. Everything runs locally in your browser, so the tool is fast, works offline once loaded, and never uploads or stores any figure you enter.

Fuel Economy Converter Formula & Method

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