Driver tools Fuel economy calculator

  • Fuel calculator to work out your car's true fuel economy
  • Find the cheapest fuel in your local area
  • Why you shouldn't always trust your trip computer
  • Work out how much you're paying for journeys

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How efficient is your car?

Fuel prices are as high as ever, so it’s important to make sure you’re getting cheap fuel — and plenty of miles for your money. 

Our simple fuel economy calculator lets you check how efficient your car really is — and whether it matches the manufacturer’s claimed fuel economy figures.

Get access to real-world fuel economy figures in our car reviews - sign up to Which? for just £1 

You can also use it to calculate the cost of individual journeys, which will help you decide whether you should take the car or opt for a cheaper mode of transport in future.

To get started, just enter the amount you paid for a litre of fuel when you last filled up. 

Then, enter the amount of fuel you purchased (in litres) and the total number of miles you covered with that fuel. 

You’ll then be presented with two figures, one showing the total cost of your journey and another showing your car’s fuel economy in miles per gallon (mpg).

If your car has a trip computer, be wary of the economy figure displayed. It's often inaccurate, so it's a good idea to get into the habit of resetting your odometer (mileometer or trip meter) after every fill. 

That way, you can record your mileage and the amount of fuel used at the next fill-up. Simply enter both figures into the fuel calculator to find out your true fuel economy.

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