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How to Convert Fuel Economy (MPG, L/100km, km/L)

Understand the different fuel economy units, why conversion is not a simple factor, and how to compare them.

Open the Fuel Economy Converter

A fuel economy converter translates between US MPG, UK MPG, litres per 100 km, and kilometres per litre. The catch is that some units are distance-per-volume (higher is better) while others are volume-per-distance (lower is better).

Distance-per-volume vs. volume-per-distance

MPG (miles per gallon) and km/L measure how far you go on a fixed amount of fuel — a higher number is better. L/100km measures how much fuel you burn over a fixed distance — a lower number is better. Converting between the two requires a reciprocal, not a simple multiplication.

Key conversion factors

  • 1 US gallon = 3.78541 L; 1 UK gallon = 4.54609 L.
  • US MPG to L/100km: 235.215 ÷ MPG.
  • L/100km to US MPG: 235.215 ÷ (L/100km).
  • US MPG to km/L: MPG × 0.425144.

How to use the converter

  1. Enter a value and choose its unit.
  2. Choose the target unit.
  3. Read the converted economy figure.

Examples

30 US MPG = 7.84 L/100km = 12.75 km/L. A car rated at 6 L/100km achieves about 39.2 US MPG. Note that 30 UK MPG (larger gallon) equals about 9.4 L/100km — a different result from US MPG.

When a fuel economy converter is useful

  • Comparing car specs across regions.
  • Estimating fuel costs for a trip.
  • Converting between US and UK figures.
  • Understanding vehicle efficiency labels.

Put it into practice

Use the Fuel Economy Converter right now — free, in your browser, no sign-up required.

Try the Fuel Economy Converter

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