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Fuel Economy Converter

MPG (US/UK), km/L and L/100 km with inverse handling.

Best for: Use it to compare a car's efficiency across US, UK and metric figures.

Complete guide

Input

From
To
How it's calculated & sources
The Fuel Economy Converter uses the standard, deterministic formula, so the same inputs always produce the same result. It runs entirely in your browser, so your inputs are never uploaded. Last reviewed June 2026.

Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.

How it works

L/100 km is inverse: km/L = 100 / (L/100 km). 1 mpg (US) ≈ 0.425 km/L.

Example

30 mpg (US) ≈ 12.75 km/L ≈ 7.84 L/100 km.

Frequently asked questions

Is conversion real-time?+

Yes — values update instantly as you type in either field, with full bidirectional input.

Where does the fuel economy reference come from?+

All factors are SI-anchored using internationally accepted conversions.

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Complete guide

Quick answers

Short, sourced answers to the questions people (and AI assistants) ask most.

What is Fuel Economy?
A fuel economy converter changes efficiency between miles per gallon (US and UK), litres per 100 km and kilometres per litre.
Why does Fuel Economy matter?
The same efficiency in your target unit. Remember MPG and km/L (higher is better) are the inverse of L/100km (lower is better).
How is Fuel Economy calculated?
MPG and km/L (distance per fuel) are inverses of L/100km (fuel per distance), so the tool inverts as needed via a common base. Formula: L/100km = 235.215 / mpg(US); km/L = mpg(US) x 0.42514; US gallon = 3.785 L, UK gallon = 4.546 L.
What are common fuel economy mistakes?
Mixing US and UK gallons - the UK gallon is about 20% larger.
When should you use the Fuel Economy Converter?
Use it to compare a car's efficiency across US, UK and metric figures.

What is the Fuel Economy Converter?

A fuel economy converter changes efficiency between miles per gallon (US and UK), litres per 100 km and kilometres per litre.

How the Fuel Economy Converter works

MPG and km/L (distance per fuel) are inverses of L/100km (fuel per distance), so the tool inverts as needed via a common base.

L/100km = 235.215 / mpg(US); km/L = mpg(US) x 0.42514; US gallon = 3.785 L, UK gallon = 4.546 L

US MPG to L/100km

2011.76
307.84
405.88
504.70

Common mistakes to avoid

  • Mixing US and UK gallons - the UK gallon is about 20% larger.
  • Treating MPG and L/100km as if they scale the same way (they are inverse).
  • Comparing MPG figures from different test cycles.

Keywords: fuel, mpg, economy.

Reviewed by the Free Tools Galaxy editorial team · Updated June 2026 · Calculated privately in your browser.

Frequently asked questions

Is the Fuel Economy Converter free to use?+

Yes. Every tool on Free Tools Galaxy is 100% free, runs in your browser and requires no signup.

How accurate is the Fuel Economy Converter?+

Fuel Economy Converter uses the standard fuel economy formula in double-precision arithmetic, so the same inputs always produce the same result and you can verify any figure by hand. It is an educational estimate — real-world outcomes depend on your actual rates, rules and assumptions.

Do you store my inputs?+

No. The Fuel Economy Converter runs entirely in your browser. Nothing is uploaded or saved to a server.

Can I use the Fuel Economy Converter on mobile?+

Yes — the interface is fully responsive and works on phones, tablets and desktops.

What are common mistakes to avoid?+

The most frequent mistake is mixing units. Double-check your inputs use a single, consistent unit before clicking Calculate.

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Title: I built/used this free fuel economy converter — instant, no signup

Body: MPG (US/UK), km/L and L/100 km with inverse handling. Try it: https://freetoolsgalaxy.com/tools/fuel-economy-converter
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Fuel Economy Converter on Free Tools Galaxy — MPG (US/UK), km/L and L/100 km with inverse handling. https://freetoolsgalaxy.com/tools/fuel-economy-converter
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# Fuel Economy Converter — the free tool I keep coming back to

MPG (US/UK), km/L and L/100 km with inverse handling.

Try it: https://freetoolsgalaxy.com/tools/fuel-economy-converter
Quora answer
The fastest way is to use a free in-browser fuel economy converter: https://freetoolsgalaxy.com/tools/fuel-economy-converter. MPG (US/UK), km/L and L/100 km with inverse handling.

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I built a free fuel economy converter that works instantly in the browser — no signup, no ads in your face
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Hey r/[subreddit],

I kept needing a quick fuel economy converter and most options online were slow or behind paywalls, so I built one that:

• Runs 100% in your browser (your data never leaves your device)
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• Loads in under a second on mobile

It covers the standard fuel economy use cases (fuel, mpg, economy) and links out to the formula + worked examples if you want to learn the math.

Link: https://freetoolsgalaxy.com/tools/fuel-economy-converter

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