Fuel Cost Calculator

Enter your car's MPG and the miles you drive to see what fuel costs a year, a month, a mile and a trip. Petrol, diesel and electric, with official UK prices already filled in.

How do I work out fuel cost per mile?

Divide your MPG into 4.54609 litres, then multiply by the price per litre. At 40 mpg a car uses 0.114 litres a mile. At 174.88p a litre, the UK average petrol price for the week commencing 5 October 2026, that is 19.9p a mile.

Work out your fuel cost

Optional. We use the reg to pick petrol, diesel or electric. DVLA does not hold MPG.

Fuel type

Find it in the handbook or the official figure for your model. US MPG figures are lower than UK ones for the same car, because a US gallon is smaller.

Default: 174.88p, the UK average pump price for the week commencing 5 October 2026 (DESNZ). Change it to the price at your pump.

For the cost of a single journey.

Fill in the boxes above and the cost appears here.

Worked example

A petrol car that does 40 mpg and drives 8,000 miles a year, with petrol at 174.88p a litre:

  • Gallons used: 8,000 miles divided by 40 mpg is 200 gallons.
  • Litres used: 200 gallons times 4.54609 is 909.2 litres.
  • Cost a year: 909.2 litres at 174.88p a litre is £1,590.04.
  • That is £132.50 a month and 19.9p a mile.

An electric car doing 3.5 miles per kWh over the same 8,000 miles uses 2,286 kWh. At 26.32p per kWh that is £601.60 a year, or 7.5p a mile. These are examples, not figures for a particular car.

Running costs are part of the price

Fuel is the biggest running cost for many drivers, but not the only one. Work out the road tax for a car by reg too, and run a history check before you buy so a hidden problem does not add to the bill.

Frequently Asked Questions

Common questions about fuel costs on Carhealth

Divide the miles per gallon into 4.54609 litres to get litres per mile, then multiply by the price per litre. At 40 mpg a car uses 0.114 litres a mile. At 174.88p a litre, the UK average petrol price for the week commencing 5 October 2026, that is 19.9p a mile.

A UK (imperial) gallon is 4.54609 litres. This calculator uses that figure. A US gallon is smaller, at about 3.785 litres, so US MPG figures look lower than UK ones for the same car. Multiply a US figure by about 1.2 to get the UK figure.

Look in the handbook, or find the official figure for your model from the manufacturer. DVLA does not record MPG, so entering a reg does not fill it in. Real-world MPG often differs from the official figure, so for the closest answer, fill the tank, note the miles on the trip meter, then fill up again and divide the miles by the gallons you added.

It starts with the UK average pump prices from DESNZ's weekly road fuel prices on GOV.UK: 174.88p a litre for unleaded petrol and 199.52p for diesel, for the week commencing 5 October 2026. DESNZ updates them every week and we refresh the defaults from time to time, so type in the price at your pump for the most accurate answer.

Multiply the kWh you use by the price per kWh. The default is 26.32p per kWh, the Ofgem price cap unit rate for 1 October to 31 December 2026. At 3.5 miles per kWh and 8,000 miles a year, that is £601.60 a year. Your own tariff and public chargers will cost a different amount per kWh, so change the price to match.

A litre of diesel costs more than a litre of petrol at the pump (199.52p against 174.88p in the week commencing 5 October 2026). Diesel cars often get more miles from each litre, so compare the cost per mile for the two cars you are choosing between rather than the price per litre.

It covers fuel or electricity only. Road tax, insurance, servicing, tyres and depreciation are extra. Our road tax calculator works out the tax for a car by reg.

Sources

Know the car before you pay for it

Fuel is easy to estimate. Finance owed, write-off history and clocked mileage are not. A Carhealth report checks them for you in about 60 seconds.

Check a car from £9.99