L/100km to MPG Converter
Turn litres per 100 km into miles per gallon and say which gallon you mean. Lower L/100 km is better; higher MPG is better. Eight L/100 km is about 29.40 US MPG or 35.31 Imperial MPG — the same car, two different gallons.
Updated
How to use
- Enter consumption in L/100 km from the handbook or a trip computer.
- Choose US liquid gallon (EPA, US pumps) or Imperial gallon (older UK mpg).
- Read MPG to two decimals. Zero or negative L/100 km is rejected (infinite MPG is not shown).
- Use the inverse converter if you start from MPG. Use Fuel Cost when you need litres and a price, not a unit change.
How it works
L/100 km asks how much fuel a distance drinks. MPG asks how much distance a gallon buys. They move in opposite directions, so a “better” car is a smaller metric number and a larger imperial-style number. The algebra uses exactly 1.609344 km per mile and one of two gallon sizes: 3.785411784 L (US liquid) or 4.54609 L (Imperial). The Imperial gallon is larger, so Imperial MPG is always higher for the same consumption.
Mixing the gallons is the usual error. A US window sticker of “30 mpg” is not 30 Imperial mpg. Treat a European 8 L/100 km as US MPG when you meant Imperial and the number looks about 20% too thirsty. This page labels the result so the two cannot hide behind a bare “MPG.”
Zero L/100 km would be infinite miles per gallon. The converter refuses it instead of printing Infinity. Negative consumption is not a physical figure. The page does not know whether your trip computer used the WLTP cycle, EPA, or a tank fill — it only converts the number you type.
This is not a cost tool. Litres for a journey still need distance and price on Fuel Cost or Road Trip Cost. Those pages want L/100 km, so you may convert MPG here only if you are going the other way on the sister page.
Brochures sometimes print both figures already. If they disagree with this converter, check which gallon and which test cycle they used. The constants on this page are the legal litre sizes, not a dynamometer.
Formula
MPG = (100 × litres per gallon) ÷ (L/100 km × 1.609344 km/mile)
Worked examples
8 L/100 km in US MPG
8 L/100 km, US gallon → 29.40 US MPG
The same figure in Imperial MPG
8 L/100 km, Imperial gallon → 35.31 Imperial MPG
Useful notes
- US MPG and Imperial MPG are labelled separately. Do not mix them.
- This is a unit conversion, not a trip cost. Use Fuel Cost for litres and price.
- Zero L/100 km is undefined as MPG and is rejected.
FAQ
- Is US MPG the same as UK MPG?
No. UK (Imperial) gallons are larger, so Imperial MPG numbers are higher for the same car.
- Why can’t I enter 0 L/100 km?
That would be infinite miles per gallon. The inverse is undefined, so the tool shows an error instead of Infinity.
- Which gallon should I pick?
US gallon for EPA-style figures and US pump gallons. Imperial for older UK mpg quotes that used the 4.54609 L gallon.
- Why is Imperial MPG higher than US MPG?
The Imperial gallon is larger (4.54609 L vs about 3.785 L), so the same litres cover more of those bigger gallons’ worth of miles.
- Does this estimate my next tank?
No. It only converts a consumption figure. Distance and price belong on Fuel Cost.
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