Fuel consumption worldwide: units and conversion
L/100km, mpg (US), mpg (UK) and km/l explained
In Germany and across Europe, liters per 100 kilometers (L/100km) is the standard. The EU legally mandates this unit for new passenger cars. A value of 7 L/100km means the vehicle consumes 7 liters of fuel over 100 kilometers. The lower the value, the more economical the vehicle. Since the introduction of the WLTP test cycle (2018), official manufacturer figures are closer to real-world driving, but are still stated in L/100km.
The US uses miles per gallon (mpg) – specifically the US gallon (3.785 liters). A higher mpg value means lower consumption. The conversion uses the formula mpg_US = 235.215 ÷ (L/100km). This means: 7 L/100km equals 33.6 mpg, and 10 L/100km equals 23.5 mpg. Since 2011, new vehicles in the US must also state combined consumption as an L/100km equivalent (MPGe for electric vehicles).
The United Kingdom also officially uses mpg, but based on the imperial gallon (4.546 liters). Because the imperial gallon is larger than the US gallon, UK mpg figures for the same vehicle are higher: 7 L/100km → 33.6 mpg (US), but 40.4 mpg (UK). Anyone buying a used car from the UK or reading UK travel reports should keep this difference in mind. Since Brexit, the UK continues to use mpg (UK) alongside L/100km.
In Japan, India and many Asian countries, km/l (kilometers per liter) is common. This is the direct inverse of L/100km: km/l = 100 ÷ (L/100km). A value of 14.3 km/l therefore corresponds to 7 L/100km. For expats, imported vehicles and international vehicle comparisons, knowing all the units matters. The calculator converts all four units into each other with high precision – the formulas are based on the exact NIST definitions for the gallon and the mile.
The non-linearity of the conversion has practical consequences: at low consumption (2–4 L/100km, hybrids, city cars), small savings lead to large mpg improvements. At high consumption (12–15 L/100km, SUVs, vans), mpg jumps are comparatively small. That is why mpg-based fuel-saving comparisons are often misleading – L/100km is the clearer unit for direct consumption comparisons.