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30.00MPG (US)
36.03MPG (UK)
12.75km per liter
7.84L per 100 km
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How it works

  1. Enter a trip, or a known value

    Use "From a trip" with a distance and fuel amount, or "Convert units" with an economy figure you already have.

  2. Pick your units

    Miles/US gallons or kilometers/liters for trip mode; any of the four common units for direct conversion.

  3. Read all four units at once

    US mpg, UK mpg, km per liter, and L per 100 km all update together.

Gas Mileage Calculator converts between the four fuel-economy units used around the world — miles per US gallon, miles per imperial (UK) gallon, kilometers per liter, and liters per 100 kilometers — and can compute any of them directly from a trip's distance and fuel used.

All four describe the same underlying quantity (how far a given amount of fuel takes you), so every conversion here routes through a single common unit — kilometers per liter — rather than converting between all six possible unit pairs directly. That's also why US and UK mpg differ for an identical car: the imperial gallon is roughly 20% larger than the US gallon, so the same fuel efficiency produces a noticeably larger "miles per gallon" number under the UK definition.

Liters per 100km runs on an inverted scale from the other three — a smaller number means better efficiency, since it's measuring fuel consumed over a fixed distance rather than distance covered per fixed fuel volume. Converting to and from it is a simple reciprocal (100 divided by km-per-liter), but it's easy to misread if you're used to "bigger is better" from mpg.

FAQ

Why is US mpg always a smaller number than UK mpg for the same car?
An imperial (UK) gallon holds about 4.55 liters versus about 3.79 liters for a US gallon. Since "miles per gallon" counts distance against a larger unit of fuel in the UK, the same car reports a higher mpg number under the UK definition even though nothing about the car changed.
Why is liters per 100km a different scale from the others?
MPG and km/L both measure distance per fixed fuel amount, so higher is better. L/100km measures fuel consumed per fixed distance, so lower is better — it's the inverse relationship, which is why it doesn't sit on the same "bigger number, more efficient" scale as the other three.
Can I compute economy directly from a fill-up?
Yes — the "From a trip" tab takes the distance you drove and the fuel you used (in either miles/gallons or kilometers/liters) and converts the resulting ratio into all four common units at once.
Is my data sent anywhere?
No. All conversions run locally in your browser.