Fuel Economy Converter

Divide 235.214 by the mpg (US) value. For example, 30 mpg = 235.214 / 30 = 7.84 L/100km. For UK mpg, divide 282.481 instead (since the UK gallon is larger).

Lower L/100km is better — it means less fuel used per 100 km. Higher mpg is also better (more miles per gallon). They are inversely related: you cannot convert them by simple multiplication.

A UK gallon (imperial) is larger than a US gallon: 1 UK gallon = 1.20095 US gallons = 4.54609 L. So UK mpg figures are always about 20% higher than US mpg for the same car. A 40 mpg (UK) car = 33.3 mpg (US) = 7.06 L/100km.

In the US: above 30 mpg is good; 40+ mpg is excellent (hybrids/efficient compacts). In L/100km terms: below 7 L/100km is good; below 5 L/100km is excellent. Electric vehicles are rated in MPGe (miles per gallon equivalent).

Fuel cost = (Trip distance / fuel economy) × fuel price. Example: 300-mile trip in a 30 mpg car at $3.50/gallon → (300/30) × $3.50 = 10 gallons × $3.50 = $35. In metric: distance (km) ÷ 100 × L/100km × price per liter.