Cost Per Mile UK

Why cost per mile matters

Cost per mile is the simplest way to compare running costs. It helps answer:

• Can I afford this commute?
• Will this car cost more to run than my current one?
• Is this deal actually good value once I include running costs?

How to work out fuel cost per mile

For a petrol or diesel car, use your real-world miles per gallon. A UK gallon is 4.54609 litres:

• litres per mile = 4.54609 ÷ mpg
• fuel cost per mile = litres per mile × price per litre

For an electric car, use miles per kWh:

• cost per mile = price per kWh ÷ miles per kWh

The government publishes the average UK pump price every week, and your electricity tariff shows your unit rate. Ofgem's price cap sets the maximum unit rate on standard variable tariffs.

Petrol cost per mile

At an illustrative 140p a litre, a petrol car doing 40 mpg uses 4.54609 ÷ 40 = 0.114 litres a mile, costing about 15.9p a mile.

Diesel cost per mile

Diesel cars often do more miles per gallon, especially on long motorway journeys, but diesel often costs more per litre. At an illustrative 149p a litre and 50 mpg, a diesel costs about 13.5p a mile. In mixed or short-trip driving the mpg advantage can shrink, which is where the saving is often overstated.

EV cost per mile

EVs vary most, because the price per kWh depends on where you charge. For an EV doing 3.5 miles per kWh, at illustrative prices:

• Home charging at an off-peak 7.5p a kWh: about 2.1p a mile
• Public rapid charging at 65p a kWh: about 18.6p a mile

Most comparisons assume home charging. If you rely on public chargers, an EV can cost more per mile than petrol. Public EV charging costs explains why.

Example at 10,000 miles

Using the same illustrative prices, fuel or electricity for 10,000 miles costs:

• Petrol (40 mpg, 140p): about £1,591
• Diesel (50 mpg, 149p): about £1,355
• EV charged at home (3.5 miles per kWh, 7.5p): about £214
• EV on public rapid chargers (3.5 miles per kWh, 65p): about £1,857

What this does not include

Cost per mile is often quoted for fuel or electricity only. That is useful for quick comparisons, but it is not your true running cost. Once you include the rest, the real cost per mile is usually much higher:

• insurance
• vehicle tax
• servicing, MOT and tyres
• depreciation, often the biggest cost of all
• finance

In the Cost Per Mile Calculator's worked example, a car driving 10,000 miles a year costs 50p a mile once everything is included, and 15p of that is fuel.

Go further with the calculators

The Cost Per Mile Calculator works out your true cost per mile from all your annual costs. For a single journey, use the Fuel Cost Calculator, and to compare an EV with a petrol car, use the EV vs Petrol Calculator.