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.

Liters per 100km (L/100km) is the inverse fuel efficiency metric used in Europe and Australia, measuring how many liters of fuel a vehicle consumes over 100 kilometers. Lower numbers mean better efficiency — a car rated at 5 L/100km uses less fuel than one rated at 8 L/100km. This is the inverse of km/L: L/100km = 100 / km/L.