Fuel Economy Converter
Convert between MPG and L/100km for car efficiency.
⛽ Note: L/100km is inverse to mpg (lower = better). Values are approximate.
What Is This Tool?
This tool converts between fuel economy units: MPG (miles per gallon, US and UK) and L/100km (liters per 100 km). These are the two main systems for measuring vehicle fuel efficiency.
The Inverse Relationship
MPG and L/100km work in opposite directions. Higher MPG is better (more miles per gallon); lower L/100km is better (less fuel for the same distance). This is why the conversion isn't a simple multiplier — it's a reciprocal.
Approximate Conversions
- 30 MPG (US) ≈ 7.8 L/100km
- 40 MPG (US) ≈ 5.9 L/100km
- 50 MPG (US) ≈ 4.7 L/100km
- 10 L/100km ≈ 23.5 MPG (US)
- 6 L/100km ≈ 39 MPG (US)
Why US and UK MPG Differ
The US gallon (3.785 liters) is smaller than the UK imperial gallon (4.546 liters), so a UK MPG number is about 20% higher for the same efficiency. Always check which gallon a source uses before comparing.
Frequently Asked Questions
Which is more efficient, 40 MPG or 5 L/100km?
5 L/100km is better — it equals about 47 MPG (US). 40 MPG equals about 5.9 L/100km.
About the Fuel Economy Converter
The Fuel Economy Converter converts fuel economy converterfrom one unit to another using the exact internationally defined conversion factors. Type a value, choose your source and target units, and the converted result is shown instantly — no waiting, no page reload.
Manual conversion is error-prone because it means memorizing ratios (how many feet in a meter, how many pints in a liter). This tool removes that friction: the conversion factor is built in, and the math is done to full precision with no rounding until the final displayed number.
How to Use This Tool
- Enter the value you want to convert in the input field.
- Select the unit you are converting from.
- Select the unit you want to convert to.
- The converted value appears instantly. Adjust either unit to compare across the board.
- Copy the result if you need it elsewhere. Your input is never sent anywhere.
Why Use an Online Converter?
Browser-based tools like this one have a few real advantages over installed software or manual methods:
- No installation. It opens instantly in any browser, on any operating system.
- Private by default. Everything runs locally, so your data stays on your device.
- Always up to date.There's nothing to update — you always get the latest version when you load the page.
- Free and unlimited. Use it as often as you like, with no account and no caps.
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