Convert imperial MPG to litres per 100km, US MPG, and km per litre
Fuel efficiency is measured differently around the world, and this creates confusion when comparing vehicles across markets. In the UK, fuel consumption is traditionally quoted in miles per gallon (MPG), using the imperial gallon of 4.546 litres. The United States also uses miles per gallon, but their gallon is smaller at 3.785 litres, which means the same car will show a lower MPG figure in US units. Meanwhile, most of continental Europe, Australia, and many other countries use litres per 100 kilometres (L/100km), which measures how much fuel is consumed over a fixed distance rather than how far a car travels on a fixed amount of fuel. This converter bridges all three standards instantly. Whether you are reading a European car review that quotes 5.2 L/100km and want to know what that means in familiar UK MPG, or you are browsing a US car forum and need to understand their MPG figures, this tool handles every conversion in one step. It also shows kilometres per litre and miles per litre for additional context. Understanding these conversions matters when shopping for imported vehicles, comparing manufacturer claims across markets, or simply making sense of motoring journalism from different countries. A car rated at 40 imperial MPG is achieving roughly 7.1 L/100km or 33.3 US MPG -- three very different numbers that all describe exactly the same fuel efficiency. Without a converter, these figures can be misleading and make direct comparisons almost impossible.
To convert fuel efficiency between measurement systems: 1. Enter your fuel efficiency in imperial MPG (miles per gallon). This is the standard UK measurement shown on dashboard displays and in manufacturer brochures. If you know your car's official combined MPG figure, use that. For real-world MPG, check your last fill-up calculation or use a trip computer average. 2. The converter instantly displays: litres per 100 kilometres (L/100km), which is the European standard -- lower numbers mean better efficiency; US MPG, which uses the smaller American gallon; kilometres per litre (km/L), common in parts of Asia; and miles per litre, useful for quick cost calculations with UK fuel prices. 3. The bar chart compares imperial MPG, US MPG, and L/100km visually so you can see the relationship between the scales at a glance. 4. Use the results to compare vehicles across markets. For example, if a German car review claims 4.5 L/100km and a UK review of a rival claims 55 MPG, enter 55 in the converter to see the UK car achieves about 5.1 L/100km -- making the German car slightly more efficient. 5. Remember that real-world fuel efficiency typically falls 10-20% below manufacturer claims due to driving style, weather, load, and road conditions.
The conversions are based on fixed unit relationships: **Imperial gallon to litres:** 1 imperial gallon = 4.546 litres. This is the UK standard gallon, larger than the US gallon (3.785 litres). The ratio between imperial and US gallons is 1.201. **Miles to kilometres:** 1 mile = 1.60934 kilometres. This is a fixed conversion used worldwide. **MPG to L/100km:** This is an inverse relationship. MPG measures distance per unit of fuel, while L/100km measures fuel per unit of distance. The formula is: L/100km = (100 x 4.546) / (MPG x 1.60934) = 282.481 / MPG For example, 40 imperial MPG converts to 282.481 / 40 = 7.06 L/100km. **Imperial MPG to US MPG:** Because the US gallon is smaller than the imperial gallon, the same car shows a lower MPG number in US units: US MPG = Imperial MPG / 1.201 So 40 imperial MPG equals 40 / 1.201 = 33.3 US MPG. This is why American fuel economy figures always look worse than UK figures for the same car. **MPG to km/L:** This combines the gallon-to-litre and mile-to-kilometre conversions: km/L = (MPG x 1.60934) / 4.546 For 40 MPG: (40 x 1.60934) / 4.546 = 14.16 km/L. **MPG to miles/L:** A simple division that tells you how far you travel on a single litre: Miles per litre = MPG / 4.546 For 40 MPG: 40 / 4.546 = 8.80 miles per litre. This is particularly useful when fuel is priced per litre, as it is in the UK. If fuel costs 145p per litre and you get 8.80 miles per litre, each mile costs approximately 16.5 pence. Note that this converter uses exact mathematical relationships between units. The results are precise and do not involve any estimation or approximation. The only variability in real-world fuel efficiency comes from driving conditions, not from the unit conversion itself.