L/100km to MPG Converter
Convert litres per 100 kilometres to miles per gallon.
Gallon Type
US MPG
29.40 MPG
km/L
12.50 km/L
Quick Reference
| Description | L/100km | US MPG | UK MPG |
|---|---|---|---|
| Sports car (poor) | 15 | 15.68 | 18.83 |
| Average SUV | 10 | 23.52 | 28.25 |
| Average car | 8 | 29.40 | 35.31 |
| Fuel-efficient car | 6 | 39.20 | 47.08 |
| Hybrid | 4.5 | 52.27 | 62.77 |
L/100km Explained
L/100km measures how many litres of fuel a vehicle uses per 100 kilometres — lower is better. It is the standard in Europe, Australia, and most of Asia. MPG (miles per gallon) is used in the US and UK — higher is better. Formula: MPG (US) = (3.785 × 100) / (L/100km × 1.609).
Built and maintained by Meet Shah · Last updated
What this tool is used for
- Comparing a European car's fuel figure against a US-market rating.
- Converting a metric consumption figure for an audience that thinks in miles per gallon.
- Checking a fleet's metric average against a target quoted in MPG.
- Understanding a spec sheet from another market.
- Comparing two vehicles rated in different systems.
Frequently Asked Questions
- Why is this not a linear conversion?
- Because the two units are RECIPROCAL — L/100km is volume per distance, mpg is distance per volume. The relationship is mpg = 235.215 ÷ (L/100km) for US gallons. Halving fuel use does not halve the mpg figure, it doubles it.
- Which gallon does the mpg use?
- It must be stated: the US gallon gives the 235.215 constant, the imperial gallon gives 282.481. UK mpg figures are therefore about 20% higher than US ones for the same car, which is a common source of confusion in reviews.
- Why do many countries prefer L/100km?
- Because it is linear in what you actually pay. Going from 10 to 9 L/100km saves the same fuel per distance as 9 to 8, whereas the equivalent mpg steps are unequal — which makes mpg a misleading basis for comparison.
- What is the MPG illusion?
- The finding that people misjudge savings because mpg is a reciprocal. Improving a vehicle from 10 to 15 mpg saves far more fuel than improving another from 30 to 40, despite the smaller headline gain — a real policy-relevant effect.
- What are typical figures?
- Around 8 L/100km is average for a modern petrol car (29 US mpg); 5 L/100km is efficient (47 mpg); above 12 is thirsty (under 20 mpg). Electric vehicles use kWh/100km or MPGe, which is a different measure again.
- Why can these figures not be averaged across a trip?
- Because the conversion is a reciprocal, so averaging one metric does not average the other. Total fuel divided by total distance is the only correct combined figure — averaging the per-leg values overweights the short legs.
Common errors and gotchas
- Treating the relationship as linear. It is reciprocal, so equal steps in one are unequal in the other.
- Mixing US and UK gallons, which differ by about 20% and change the answer substantially.
- Assuming a lower number is worse. In L/100km lower is better, and in MPG higher is better.
- Averaging MPG figures directly, which is mathematically wrong for a reciprocal quantity.
- Comparing figures measured under different test cycles, which is a bigger difference than the conversion.
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