Fuel Economy Converter

Convert between MPG (US and UK), liters per 100 km and kilometers per liter. This free fuel consumption converter runs entirely in your browser, so your numbers never leave your device.

How to use the fuel economy converter

  1. Enter the figure. Type your car's fuel economy into the Value box — for example 8 for 8 L/100km or 30 for 30 mpg.
  2. Choose the units. Set the unit you have in the From menu and the unit you want in the To menu. Press ⇄ to swap them instantly.
  3. Read the converted value. The answer updates as you type, and the table underneath shows the same economy in every supported unit.

About this tool

Fuel economy is measured differently around the world, which makes comparing cars confusing. The United States quotes miles per gallon using the smaller US gallon (3.785 L), the United Kingdom uses miles per gallon with the larger Imperial gallon (4.546 L), and most of the rest of the world uses either liters per 100 kilometers or kilometers per liter. Because a US gallon is smaller than a UK gallon, the same car always shows a lower MPG figure in US units than in UK units — a real difference of about 20 percent, not a mistake.

One important subtlety is that liters per 100 km works the opposite way to the other units: a lower L/100km number means a more efficient car, while a higher MPG or km/L number means a more efficient car. That is because L/100km measures fuel used per fixed distance, whereas MPG and km/L measure distance travelled per fixed fuel. This converter handles the inverse relationship automatically. Everything is calculated locally in your browser, so nothing is uploaded and the tool works offline once loaded.

Frequently asked questions

Why is US MPG lower than UK MPG for the same car?

The US gallon (3.785 liters) is smaller than the Imperial gallon (4.546 liters). Since MPG is miles per gallon, a smaller gallon yields fewer miles, so US MPG is always about 20% lower than UK MPG for identical real-world consumption.

Is a lower or higher number better?

For MPG and km/L, higher is better — you travel further on the same fuel. For L/100km, lower is better — you burn less fuel over the same distance. The converter accounts for this automatically when you switch units.

How do I convert L/100km to MPG?

First convert to kilometers per liter by dividing 100 by the L/100km figure, then convert km/L to MPG. This tool does all of that in one step — just choose L/100km in the From box and MPG in the To box.

What is a good fuel economy figure?

It depends on the vehicle, but a modern efficient petrol car is often around 5–7 L/100km (roughly 34–47 US MPG or 40–56 UK MPG). Hybrids and small cars do better, while large SUVs and trucks use considerably more.