About the Fuel Economy Converter

Fuel economy is measured two opposite ways: distance per fuel (mpg, km/L) and fuel per distance (L/100km). The conversion constants come from the gallon definitions — 1 US gallon = 3.785 L, 1 imperial gallon = 4.546 L — and 1 mile = 1.609 km. The calculator normalizes everything to L/100km, the most precise common unit, then re-expresses it in every system.

Why the numbers matter

Consumption drives both budget and emissions. Every liter of gasoline releases about 2.31 kg of CO₂, so a car using 8 L/100km emits roughly 192 g/km — about 2.9 tonnes over 15,000 km. Improving from 8 to 6 L/100km saves over 700 liters a year, which at $1.50/L is more than $1,000 annually plus a tonne of CO₂. Small efficiency gains compound quickly.