Fuel Economy Converter
Convert fuel economy between MPG (US and UK), litres per 100 kilometres, and kilometres per litre.
Reviewed by the ToolNestr Editorial Team — July 2026
How fuel economy conversion works
Fuel economy is measured in different units around the world, but they all describe the same thing: how far a vehicle travels on a given amount of fuel. L/100km (litres per 100 kilometres) and km/L (kilometres per litre) are metric units. MPG (miles per gallon) is used in the US and UK, with the important distinction that a US gallon (3.785 L) is smaller than a UK imperial gallon (4.546 L).
The relationship between L/100km and MPG is inversely proportional — as one goes up, the other goes down. This means the conversion is nonlinear: improving from 10 to 12 MPG saves more fuel than improving from 30 to 32 MPG. This converter handles all four units simultaneously so you can see the full picture at once.
The formula explained
Worked example
Convert 8 L/100km to all units.
Car Shopping Comparison
Compare vehicles from different markets. Convert a European car's L/100km to MPG to compare with US models.
Road Trip Planning
Know your car's MPG but travelling through a country that lists fuel economy in L/100km? Convert instantly.
Fleet Management
Standardise fuel economy across a mixed fleet of US and imported vehicles into a single metric.
Efficiency Tracking
Track your car's fuel economy over time. Enter fill-up data and convert between units for your log.
How to use the fuel economy converter
Enter your value
Type the fuel economy number you want to convert, like 8 for 8 L/100km.
Choose the unit
Select whether your number is L/100km, MPG (US), MPG (UK), or km/L.
See all equivalents
All four units update instantly. Compare US MPG vs UK MPG and metric at a glance.
Tips for fuel economy
Always check which gallon
UK MPG is about 20% higher than US MPG for the same fuel efficiency. A 40 MPG UK car is only 33 MPG US. Always specify which gallon you are using.
Lower L/100km is better
Unlike MPG where higher is better, L/100km is the opposite. This inverse relationship can be confusing when switching between the two systems.
Fuel economy varies by driving
City driving typically uses 20–40% more fuel than highway cruising. Use your combined rating rather than the highway figure for accurate annual estimates.
Use L/100km for fuel cost
Most fuel cost calculators work in L/100km. Convert your MPG to L/100km first, then use it with our fuel cost calculator for accurate trip budgeting.
Related tools
Frequently asked questions
What is the difference between US MPG and UK MPG?
A US gallon is 3.785 litres while a UK (imperial) gallon is 4.546 litres. A car that does 30 MPG US gets 36 MPG UK.
Which fuel economy unit is most common?
L/100km is standard in Europe, Canada, Australia, and most of the world. MPG is standard in the US and UK.
Is higher or lower L/100km better?
Lower L/100km is better — it means you burn fewer litres per 100 km. For MPG, higher is better.
How do I convert L/100km to MPG?
Divide 235.215 by L/100km for US MPG. Divide 282.481 by L/100km for UK MPG.
What is a good fuel economy?
Under 6 L/100km (39+ MPG) is excellent, 6–8 L/100km (29–39 MPG) is average, over 10 L/100km (under 24 MPG) is poor.