About this calculator
The L/100km Calculator converts fuel economy into litres per 100 kilometres and can also convert between L/100km and UK MPG. L/100km is common in Europe and many technical specifications. Unlike MPG, lower L/100km is better because it means fewer litres are needed to travel 100km.
L/100km Calculator method
This calculator uses straightforward fuel economy, vehicle measurement, or unit conversion formulas. Results are estimates for planning and comparison, so real-world driving, vehicle condition, load, weather, route type, and manufacturer data can change the outcome.
- L/100km = litres used / kilometres travelled x 100
- UK MPG = 282.481 / L/100km
- L/100km = 282.481 / UK MPG
How to use the L/100km Calculator
- Enter the main vehicle or journey figures requested by the calculator.
- Use UK units where shown, especially miles, litres, UK MPG, and prices per litre.
- Check whether the calculator is asking for measured real-world figures or official brochure figures.
- Review the headline result and the supporting breakdown below it.
- Compare at least two scenarios if you are choosing between vehicles, journeys, or running-cost assumptions.
- Adjust one assumption at a time to see which input changes the result most.
- Use the result as an estimate, then confirm important decisions with real quotes, vehicle records, or specialist advice.
Worked examples
Measured fuel use
Input: 35 litres used over 560km
Calculation: 35 / 560 x 100
Result: 6.25 L/100km
Convert from UK MPG
Input: 50 UK MPG
Calculation: 282.481 / 50
Result: About 5.65 L/100km
Reading L/100km correctly
MPG and L/100km move in opposite directions. Higher MPG is better, but lower L/100km is better. This is a common source of mistakes when comparing UK and European vehicle information.
Useful reference points
| UK MPG | Approx L/100km |
|---|---|
| 30 MPG | 9.42 |
| 40 MPG | 7.06 |
| 50 MPG | 5.65 |
| 60 MPG | 4.71 |
Why real-world results vary
Fuel economy and running costs can shift noticeably from the calculated result. Short trips, cold starts, roof boxes, tyre pressure, motorway speed, stop-start traffic, heavy loads, air conditioning, and poor servicing can all increase fuel use.
For buying decisions, compare a conservative scenario as well as an optimistic one. A car that looks cheaper on official MPG may cost more if your real-world driving pattern is mainly urban or short-distance.
Common mistakes and edge cases
- Lower L/100km is better; higher MPG is better.
- Use kilometres with L/100km, not miles.
- Use UK MPG for the built-in conversion unless comparing US data separately.
- Rounding can create small differences between published tables and calculated results.
Limitations
This calculator is for general information only. It is not financial, engineering, insurance, valuation, or mechanical advice.
- The calculator assumes accurate fuel and distance measurements.
- It does not adjust for route type, vehicle load, tyre pressure, or weather.
- It is not a certification or emissions test.
Frequently asked questions
Is 5 L/100km good?
For many petrol or diesel cars it is efficient, but the meaning depends on vehicle size, fuel type, and driving pattern.
Why do European sites use L/100km?
It directly states how much fuel is consumed to travel a fixed distance.
Can I convert MPG to L/100km?
Yes. For UK MPG, divide 282.481 by the MPG figure.
Can I use US MPG?
Not directly with the UK conversion constant. US MPG uses a smaller gallon.
Which is easier for cost?
Litres used is easiest for cost because UK fuel is sold in litres.
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