Free Online Fuel Consumption Converter

Fuel economy mixes reciprocal and linear units: L/100km = 235.215 / mpg(US), and US and UK gallons differ, so a single conversion has two gotchas.

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Result
7.8405 L/100km
mpg and L/100km are reciprocal (lower L/100km = more efficient).

How to Use This Converter

  1. Pick the From unit (note the US versus UK mpg distinction).
  2. Pick the To unit in the second dropdown.
  3. Enter the value; the converter inverts the ratio automatically.
  4. Tap swap to check the reverse direction.

What Is a Fuel Consumption?

Fuel economy is one of the few everyday conversions where you also flip the direction of the ratio. mpg measures distance per fuel — higher is better. L/100km measures fuel per distance — lower is better. The two are reciprocals: L/100km ≈ 235.215 / mpg(US), or 282.481 / mpg(UK) since UK gallons are 20% larger.

Drivers comparing a US window sticker against a European one, fleet managers benchmarking trucks across regions and EV owners cross-checking MPGe against L/100km all hit this. 30 US mpg is 7.84 L/100km is 12.75 km/L; 30 UK mpg is 9.42 L/100km because a UK gallon is 4.546 L versus the US 3.785 L.

The tool handles the inverse relationship automatically and labels both gallon variants explicitly so the answer is unambiguous.

Frequently Asked Questions

How do I convert mpg to L/100km?
L/100km = 235.215 / mpg. 30 mpg ≈ 7.84 L/100km.
US vs UK gallons?
UK gallon is larger. US mpg is lower than UK mpg for same efficiency. Specify which.
What's good fuel economy?
Under 6 L/100km (40+ mpg) is efficient. Under 4 L/100km is excellent.

Published by the WeGotEveryTool team. We build and test every tool in-house and update pages when the underlying spec, formula, or recommendation changes.

Reviewed: May 2026. Disclaimer: this tool is provided as-is for general informational use. For decisions with material consequences (medical, legal, financial, security) verify results against a qualified professional source.

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