Fuel Economy Converter (MPG to L/100km)

Example

Input: 30 MPG (US)

Result: 7.84 L/100km

Step-by-Step Guide

1. Identify Source Unit

Check if your vehicle displays US MPG, UK MPG, or L/100km.

2. Input Efficiency

Enter the value from your dashboard or spec sheet.

3. Select Target

Choose the unit you wish to convert to.

4. Analyze Result

Remember: High MPG = Low L/100km.

What is Fuel Economy Converter (MPG to L/100km)?

Fuel economy standards vary globally, creating confusion for travelers and car importers. The US uses Miles Per Gallon (MPG) based on a 3.78L gallon, the UK uses MPG based on a 4.54L Imperial gallon, and most of the world uses Liters per 100km (L/100km). This converter normalizes these disparate metrics, allowing for accurate comparison of vehicle efficiency across borders. Unlike MPG, where higher is better, L/100km is an inverted metric where lower values indicate better efficiency.

How it Works

The conversion relies on fixed volumetric constants. To convert US MPG to L/100km, the formula is 235.215 / US MPG. For UK MPG to L/100km, the formula is 282.481 / UK MPG. This inverse relationship exists because one measures distance per fixed fuel unit, while the other measures fuel consumed over a fixed distance.

FAQ

Why is UK MPG higher than US MPG?

The UK Imperial gallon is approximately 20% larger (4.54 liters) than the US liquid gallon (3.78 liters), leading to higher distance numbers for the same amount of fuel.

What is a good L/100km score?

Generally, anything below 8 L/100km is considered good fuel economy for a combustion engine; hybrids often achieve less than 5 L/100km.

How do I convert EV efficiency?

Electric vehicles often use MPGe (Miles Per Gallon equivalent) or Wh/mi. 33.7 kWh of electricity is chemically equivalent to one gallon of gasoline.

Does L/100km account for idling?

Yes, because zero distance is traveled while fuel is consumed, L/100km spikes toward infinity when idling, accurately reflecting waste.

Why is L/100km the scientific standard?

It measures consumption directly (fuel used) rather than performance (distance traveled), making it easier to calculate total fuel needs for a specific journey.

Conclusion

Accurate fuel economy conversion is vital for budgeting international road trips and comparing vehicle specs globally. A car rated at 40 MPG in the UK is actually less efficient than a 35 MPG US car due to the gallon size difference. This tool eliminates that ambiguity.

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References & Standards

This calculator uses formulas and data standards from Standard References to ensure accuracy.

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