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Fuel Savings Calculator

See how much fuel, money, and percentage you save each year by switching to a more efficient vehicle.

How it is calculated

Consumption is entered in litres per 100 km for the old (eco1) and new (eco2) vehicle, distance in km per year and price per litre. litres = distance ÷ 100 × consumption for each car; litres saved = litres_old − litres_new; money saved = litres saved × price; reduction % = (eco1 − eco2) ÷ eco1 × 100. Litres are rounded to whole numbers and money is shown in dollars. The tool needs eco1 above zero. If the new car uses more fuel, the savings come out negative, which means extra cost.

Worked example

Old car 9 L/100 km, new car 6 L/100 km, 15,000 km a year, fuel at 1.8 per litre. Old: 15,000 ÷ 100 × 9 = 1,350 L. New: 150 × 6 = 900 L. Saved: 1,350 − 900 = 450 L. Money: 450 × 1.8 = $810.00 per year. Reduction: (9 − 6) ÷ 9 × 100 = 33.33%.

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Common mistakes

  • Entering miles per gallon instead of litres per 100 km; the two scales run in opposite directions, so convert first.
  • Typing monthly distance when the result is read as a yearly figure.
  • Swapping the old and new consumption, which turns a saving into a negative number.
  • Ignoring the purchase price, insurance and maintenance difference; this tool only compares fuel.
  • Using the manufacturer's rated consumption for the new car when real-world driving usually differs.

About this calculator

This calculator compares an old and a new vehicle by yearly distance driven and fuel consumption, then reports the liters saved per year, the money saved annually, and the percentage reduction in consumption between the two.

Car buyers use it to see whether a more fuel-efficient vehicle is actually worth the switch, and fleet managers use the same math to estimate savings across a group of vehicles before deciding on an upgrade.

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Comments (1)

  • Editorial team

    Consumption must be entered in litres per 100 km, so a car rated in miles per gallon needs converting first. Price per litre is a single figure, which hides the fact that the new car may take a different fuel, such as diesel instead of petrol. If it does, run the tool with each price separately. The litres shown are rounded to whole numbers. Does your comparison include a fuel type change or a mix of city and highway driving?

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