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Conversions

Fuel Economy Converter

Convert between MPG (US), MPG (UK), L/100km, and km/L fuel economy units. Compare fuel efficiency across regions.

What is Fuel Economy Converter?

A fuel economy converter lets you compare vehicle efficiency across the different standards used around the world. The US uses miles per gallon (MPG), the UK also uses MPG but with the larger imperial gallon, and most other countries use litres per 100 kilometres (L/100km) or kilometres per litre (km/L). Converting between them is essential when comparing international car specs or planning road trips across borders.

How to use

  1. 1 Enter your fuel economy value in the Value field.
  2. 2 Select the unit you are converting from in the From dropdown.
  3. 3 Select the target unit in the To dropdown.
  4. 4 The result and a full comparison table appear immediately.
  5. 5 Use the swap button to reverse the conversion direction.

Formula

All conversions go through km/L as the common base. L/100km = 100 / km/L. US MPG to km/L = value * 1.60934 / 3.78541. UK MPG to km/L = value * 1.60934 / 4.54609.

Example calculation

A car rated at 30 US MPG: 30 * 1.60934 / 3.78541 = 12.75 km/L, or 100 / 12.75 = 7.84 L/100km. The same car in UK MPG: 30 * 3.78541 / 4.54609 = 24.97 UK MPG.

Frequently asked questions

Why do US MPG and UK MPG differ for the same car?

The US gallon equals 3.785 litres while the UK imperial gallon equals 4.546 litres. The same car will show a higher MPG figure in UK units because more miles fit per larger gallon. A car getting 30 US MPG gets approximately 36 UK MPG.

Is a higher or lower L/100km better?

Lower L/100km is better because it means the car uses less fuel to travel 100 kilometres. A car using 5 L/100km is more efficient than one using 8 L/100km. This is the opposite of MPG where higher numbers are better.

How do I convert L/100km to MPG?

Use the formula: US MPG = 235.215 / L100km. For example, a car using 7 L/100km = 235.215 / 7 = 33.6 US MPG. This converter handles the calculation automatically.

What is considered good fuel economy?

For a petrol/gasoline car, under 6 L/100km (above 39 US MPG) is generally considered excellent. 7 to 9 L/100km (26 to 34 MPG) is average. Hybrid cars typically achieve 4 to 5 L/100km and electric vehicles are rated in km per kWh instead.

What is km/gallon?

Kilometres per US gallon expresses how many kilometres a vehicle travels on one US gallon of fuel. It is less common than MPG or L/100km but appears in some international contexts. 1 km/gal equals approximately 0.264 km/L or 0.425 US MPG.