Fuel Economy Converter

Convert fuel economy between MPG (US), MPG (UK), km/L, and L/100 km, with all equivalents shown at once plus range examples for common tank sizes.

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Fuel economy converter Convert MPG (US), MPG (UK), km/L, and L/100km, then compare the same efficiency against practical tank-size range examples.

Common presets

Remember the inverse unit

MPG and km/L get bigger as efficiency improves. L/100km gets smaller. That is why zero and negative values are invalid: the inverse conversion would break.

Quick checkpoints

30 mpg (US) is about 12.75 km/L and 7.84 L/100km. Lower L/100km means better efficiency, while higher MPG and km/L mean better efficiency.

Enter a fuel economy figure Provide an MPG, km/L, or L/100km value to compare the common efficiency units and tank-size range examples.

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Fuel Economy Converter

Fuel economy converter: MPG, km/L, and L/100 km explained

A fuel economy converter translates the same vehicle efficiency into the unit system your source uses. That may mean US miles per gallon for North American specs, UK miles per gallon for older British references, kilometres per litre for a direct distance-per-fuel view, or litres per 100 kilometres for the inverse metric format used across much of Europe and beyond.

Why fuel economy units are tricky

Fuel economy units do not all move in the same direction. MPG and km/L rise as a vehicle becomes more efficient, but L/100 km falls. That inverse relationship is why a converter cannot treat all fuel economy units as simple multipliers.

US and UK miles per gallon are not interchangeable either, because the gallons are different sizes. A UK gallon is larger than a US gallon, so the same car will always show a higher mpg value in UK terms than in US terms.

L/100 km = 100 / (km/L)

Metric consumption is the inverse of metric efficiency.

1 US gal = 3.785411784 L

US gallon size used in mpg (US) conversions.

1 UK gal = 4.54609 L

Imperial gallon size used in mpg (UK) conversions.

How to interpret the results

Use MPG when you are matching US or UK vehicle specifications, older road tests, or user discussions that already reference gallons. Use km/L when you want an intuitive “distance from one litre” comparison. Use L/100 km when you care about fuel consumed over a fixed trip length, which is why that format is common on labels, fleet reports, and efficiency regulations.

The range examples in the calculator are only simple distance illustrations. Real-world range still depends on driving speed, traffic, weather, tyre pressure, gradients, payload, and whether the quoted efficiency figure came from laboratory testing or observed use.

Worked examples for real vehicles

A car rated at 30 mpg (US) is roughly 12.75 km/L and about 7.84 L/100 km. With a 50-litre tank, that same efficiency suggests a nominal range of about 638 km before allowing for reserve fuel, driving style, or route conditions.

A vehicle showing 6.5 L/100 km converts to about 15.38 km/L and around 36.19 mpg (US). That can help when one review, owner forum, or dealer source uses metric consumption while another quotes MPG.

Further reading

Frequently asked questions

Why is mpg (UK) higher than mpg (US) for the same car?

Because the UK gallon is larger than the US gallon. The vehicle travels the same distance, but each imperial gallon contains more fuel, so the quoted miles-per-gallon number comes out higher.

 Is lower L/100 km better?

Yes. L/100 km measures fuel consumed over a fixed distance, so a lower number means the vehicle needs less fuel to travel 100 kilometres.

 Can I use the range examples as an exact trip forecast?

No. They are simple illustrations based on the entered efficiency and a nominal tank size. Real range changes with speed, terrain, weather, load, and how much fuel reserve you keep.

 Which unit is best for comparing cars internationally?

L/100 km and km/L are usually easiest for cross-border comparison because they avoid the US-versus-UK gallon issue. MPG is still helpful when you are matching regional spec sheets or reviews.

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