How Much Will a Car Cost to Run? UK Fuel Cost Calculator
Fuel is often the second-biggest cost of car ownership after depreciation. This guide shows you how to calculate the real running cost of any car using live UK pump prices - and lets you try the calculator right here.
Fuel Cost
Estimator
Enter your MPG and a distance to get the exact journey cost using live UK pump prices from the government Fuel Finder API.
Real-world MPG applies a 78% correction to WLTP figures. Actual consumption varies by driving style.
Enter your MPG and a distance
to calculate journey and annual fuel cost
Why fuel costs catch buyers off guard
Most buyers focus almost entirely on the purchase price. But for a car doing the UK average of 9,000 miles per year, annual fuel costs typically run from £900 for an efficient petrol or hybrid to £2,200+ for a large diesel or performance car. Over three years of ownership, that's a £4,000–£6,000 swing depending on which car you pick.
How to find a car's real-world MPG
The official WLTP figure on every car's spec sheet is measured under laboratory conditions and almost always overstates real-world economy - typically by 15–25%. AutoAlpha derives a real-world MPG estimate from the CO₂ emissions figure in the DVLA database (using the formula: MPG ≈ 235.21 / CO₂ × 0.78 correction).
For a more accurate figure, check real-world MPG databases like Honest John or Fuelly, which aggregate owner-reported figures. A car rated at 60 MPG official might do 46–50 MPG in real UK driving.
Petrol vs diesel vs hybrid: which is cheaper to run?
For low-mileage drivers (under 8,000 miles/year), petrol is usually cheapest in total once you account for the higher purchase price of diesel and hybrid models. For medium mileage (8,000–15,000), a modern diesel or self-charging hybrid often breaks even on fuel savings within 2 years. For high mileage (over 15,000), diesel or plug-in hybrid offers the best running cost by a significant margin.
Electric cars: how to calculate charging costs
EV running cost depends on whether you charge at home or publicly. Home charging at the standard tariff (around 25p/kWh) costs roughly 7p per mile for an efficient EV. Public rapid charging at 70–80p/kWh pushes that to 20–23p per mile - similar to a petrol car, and removing most of the cost advantage. If you don't have home charging, factor this into your real-world running cost.
Check if the car is worth buying at all
After you've estimated running costs, use AutoAlpha to check whether the asking price is fair against the live market.
Run a free price check →No account needed · Live the UK's leading car marketplace data