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Convert Fuel Economy Between MPG, km/L and L/100km Convert between MPG (US), MPG (UK), km/L, and L/100km fuel economy ratings.

Fuel Economy Converter illustration
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Fuel Economy Converter

Convert between MPG (US), MPG (UK), km/L, and L/100km fuel economy ratings.

1

Enter a fuel economy value

Type the fuel economy value.

2

Select units

Choose source and target fuel economy units.

3

Read the converted fuel economy

Converted fuel economy appears instantly.

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What Is Fuel Economy Converter?

A fuel economy converter translates between different ways of expressing vehicle fuel efficiency. The US uses miles per gallon (MPG using US gallons), the UK uses MPG with Imperial gallons (20% larger), Europe and most of the world use liters per 100 kilometers (L/100km), and some Asian markets use kilometers per liter (km/L). Notably, L/100km is an inverse scale — lower values mean better efficiency — while MPG and km/L are direct scales where higher values mean better efficiency. This converter handles the inverse math correctly.

Why Use Fuel Economy Converter?

  • Handles the tricky inverse conversion between MPG and L/100km.
  • Distinguishes US and UK gallons (a 20% difference!).
  • Essential for comparing cars across different markets.
  • Real-time conversion with reference table.

Common Use Cases

Car Shopping

Compare fuel economy ratings from US, UK, and European markets.

Travel

Understand fuel costs when renting cars abroad.

Fleet Management

Normalize vehicle efficiency readings across internationally sourced fleets.

Environmental Analysis

Standardize fuel consumption data across different reporting systems.

Technical Guide

Fuel economy systems:

• MPG (US): miles per US gallon (1 gal = 3.785 L)
• MPG (UK): miles per Imperial gallon (1 gal = 4.546 L)
• km/L: kilometers per liter (direct)
• L/100km: liters per 100 kilometers (inverse — lower is better)

Conversion formulas:
• MPG (US) to km/L: multiply by 0.4251
• MPG (US) to L/100km: divide 235.215 by MPG
• km/L to L/100km: divide 100 by km/L

The inverse nature of L/100km makes mental math tricky. At high MPG values, small MPG changes matter less in absolute fuel consumption. For example, improving from 10 to 15 MPG saves much more fuel than improving from 30 to 35 MPG for the same distance.

Tips & Best Practices

  • 1
    US vs UK MPG: a car rated 30 MPG(US) = 36 MPG(UK) due to the larger Imperial gallon.
  • 2
    Quick L/100km to MPG(US): divide 235 by L/100km. Example: 8 L/100km ≈ 29 MPG.
  • 3
    L/100km is inverse: lower = better. 5 L/100km is more efficient than 10 L/100km.
  • 4
    Electric cars are rated in kWh/100km or MPGe (miles per gallon equivalent).

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Frequently Asked Questions

Q How do I convert MPG to L/100km?
Divide 235.215 by the MPG (US) value. For example, 30 MPG ≈ 7.84 L/100km.
Q Why are US and UK MPG different?
They use different gallon sizes. The US gallon is 3.785 L while the Imperial (UK) gallon is 4.546 L, making UK MPG values about 20% higher for the same car.
Q What is a good L/100km rating?
Under 6 L/100km is considered efficient for a sedan. Hybrids often achieve 4-5 L/100km. SUVs typically range 8-12 L/100km.
Q Is L/100km better than MPG?
L/100km is arguably more intuitive for cost calculations (fuel consumed per distance), while MPG emphasizes distance per fuel unit. Engineers generally prefer L/100km for its linear relationship to fuel consumption.
Q What does 35 MPG(US) equal in L/100km?
235.215 ÷ 35 ≈ 6.72 L/100km.

About This Tool

Fuel Economy Converter is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.