Kilometers per liter (km/L) is the standard fuel efficiency metric used in most countries outside the US and UK, measuring how far a vehicle travels on one liter of fuel. A typical compact car achieves 12–18 km/L, while hybrids can exceed 25 km/L. One km/L equals approximately 2.352 miles per US gallon.

Miles per gallon UK (imperial mpg) measures distance per imperial gallon (4.546 liters), used in the United Kingdom for fuel economy ratings. Because the imperial gallon is larger than the US gallon, the same car shows a higher mpg figure in the UK system. One UK mpg equals approximately 0.354 km/L or about 28.25 L/100km.