Fuel Economy Converter
Convert fuel economy between US MPG, UK (imperial) MPG, kilometers per liter and liters per 100 km. Compare your car's efficiency in any unit. Free, private, accurate.
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Convert fuel economy units
Fuel economy is measured in genuinely different ways around the world, and comparing a figure from one country against another requires careful conversion. This converter moves between US MPG, UK imperial MPG, kilometres per litre and litres per 100km, so you can compare any car’s economy on a like-for-like basis rather than being misled by the units.
Why the units are not interchangeable
Fuel economy is expressed as distance per unit of fuel (MPG, km/L) in some places and as fuel per fixed distance (L/100km) in others, and crucially the two are inverses of one another, so a higher number is better for the first while a lower number is better for the second. To make things worse, the US and UK gallons are actually different sizes, which means US MPG and UK MPG are not the same figure even for the identical car. Comparing a vehicle’s economy across all these systems therefore requires converting correctly, which is exactly where casual side-by-side comparisons quietly go wrong. The converter handles both the gallon difference and the inverse relationship so that the figures genuinely compare.
A calculation, not advice
It runs entirely in your browser, so nothing you enter is uploaded and it works without an account, keeping your figures on your own machine and available on any device immediately.
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Frequently Asked Questions
Why do US and UK MPG differ?
Because the US and imperial gallons are different sizes, so the same car has a different MPG figure in each system. They are not interchangeable.
What is the difference between MPG and L/100km?
MPG is distance per fuel (higher is better); L/100km is fuel per distance (lower is better). They are inverses of each other.
Which units does it convert?
US MPG, UK imperial MPG, kilometres per litre, and litres per 100km, handling the gallon difference and the inverse relationship.
Why is comparing economy error-prone?
Because the systems mix inverse measures and different gallon sizes, so a naive comparison gets it wrong. The converter makes them comparable.
Is my data uploaded?
No. The conversion runs entirely in your browser.
Privacy & Security
All processing happens locally in your browser — nothing is uploaded.
How to Use
Enter a value and its unit; all fuel-economy units are converted instantly.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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