Miles per Gallon (US) to Liters per 100 km Converter

Window stickers, US reviews and trip computers set to imperial units give economy in miles per gallon. Many other countries compare cars in L/100km. This page assumes the mpg you type is US mpg:

• 25 mpg = 9.4086 L/100km
• 30 mpg = 7.8405 L/100km
• 35 mpg = 6.7204 L/100km
• 40 mpg = 5.8804 L/100km

If your figure is from a UK source, set the From menu to Miles per Gallon (UK) first. 40 UK mpg is 7.062 L/100km, noticeably worse than 40 US mpg, because the UK gallon holds more fuel.

Because mpg counts distance rather than fuel, its gains are misleading at the top end. Look at the fuel each car uses over 1,000 miles:

A 10 mpg improvement on a thirsty truck saves far more fuel than a 20 mpg improvement on an already efficient car. In L/100km the picture is honest: 10 mpg is 23.5215 and 20 mpg is 11.7607, a drop of almost 12 L/100km, while 30 to 50 mpg is 7.8405 to 4.7043, a drop of about 3.1. Converting to L/100km is the easiest way to see which upgrade actually matters.

Divide 235 by the US mpg figure. 235 ÷ 35 = 6.714, while the converter gives 6.7204, a difference of 0.09%. For UK mpg, divide 282 instead. No multiplier turns mpg into L/100km, because the conversion is a reciprocal. A spreadsheet column that multiplies mpg by a fixed factor will be wrong for every row except one.

Once a figure is in L/100km, cost per distance is one multiplication: litres per 100 km times the price of a litre. At a price of 1.50 per litre in any currency, a 30 mpg car (7.8405 L/100km) costs about 11.76 per 100 km and a 25 mpg car (9.4086 L/100km) about 14.11. That is a cleaner way to compare two cars than the gap between their mpg numbers.