Fuel Economy Converter (MPG, L/100km, km/L)
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Fuel economy is measured differently around the world: the US uses miles per gallon (US gallon), the UK uses miles per gallon (Imperial gallon), most of Europe uses litres per 100 km, and many other countries use kilometres per litre. Because L/100km measures consumption (lower is better) while the others measure distance per fuel (higher is better), converting between them is not a simple multiplication — it involves reciprocals. This tool handles all of that: enter a value in any one unit and it instantly shows the equivalent in the other three, using the exact gallon and mile definitions (1 US gallon = 3.785411784 L, 1 Imperial gallon = 4.54609 L, 1 mile = 1.609344 km). Everything runs locally in your browser — nothing is uploaded.
How to use
- Enter a fuel-economy value.
- Pick the unit it is given in.
- Read the equivalent in the other three units; the input unit is highlighted.
- Try 30 MPG (US) — it is about 7.84 L/100km and 12.75 km/L.
Frequently asked questions
- Why isn't US MPG the same as Imperial MPG?
- The two use different gallons. A US gallon is 3.785 L while an Imperial (UK) gallon is 4.546 L — about 20% larger — so the same car shows a higher number in Imperial MPG than in US MPG.
- Why is converting to L/100km not just a fixed multiplier?
- MPG and km/L are 'distance per fuel' (more is better) while L/100km is 'fuel per distance' (less is better). They are inversely related, so the conversion uses a division: L/100km = 235.215 ÷ MPG(US), for example.
- Which gallon and mile values are used?
- Exact international definitions: 1 US gallon = 3.785411784 L, 1 Imperial gallon = 4.54609 L, 1 mile = 1.609344 km. Results are rounded to four decimal places.
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