Cost Per Mile Calculator

Work out your cost per mile

Enter your car's average miles per gallon and the pump price per litre into the calculator above. It returns your fuel cost per mile in pence, which is the number most people actually want. If you also know your wider yearly motoring costs, read on for the full running-cost method below.

How the maths works

Fuel is sold in litres in the UK, but economy is still quoted in miles per gallon. One UK gallon is 4.546 litres, so the calculation has to bridge those two units. The plain-English formula is:

Cost per mile = (litres per gallon × price per litre) ÷ miles per gallon

In other words, you first work out what a full gallon costs at today's pump price, then divide that by how many miles that gallon takes you. Multiply the answer by 100 to read it in pence per mile rather than pounds.

Written as a two-step sum it looks like this:

• Cost per gallon = 4.546 × price per litre
• Pence per mile = (cost per gallon ÷ mpg) × 100

That is all the fuel side needs. The reason a smaller car feels so much cheaper on a long trip is baked into the second division: at 60 mpg you spread the cost of that gallon over far more tarmac than you do at 30 mpg, so your pence-per-mile roughly halves.

A quick word on mpg itself. The figure on a manufacturer's brochure is a lab number and rarely matches real life. For an honest cost per mile, use your own observed economy: note your mileage at a fill-up, drive normally, then divide the miles covered by the litres you put in at the next fill (remembering to convert litres to gallons). Real-world economy on motorways, in winter, or with a roof box can sit 15-25% below the brochure claim.

Worked example: a petrol commuter

Say you drive a petrol hatchback that genuinely returns 45 mpg, and the pump price is £1.40 a litre.

• Cost per gallon = 4.546 × £1.40 = £6.36
• Pence per mile = (£6.36 ÷ 45) × 100 = 14.1p per mile

Your 24-mile round-trip commute therefore costs about 24 × 14.1p = £3.38 in fuel each day, or roughly £760 across a 225-day working year. Seeing it as a single annual number often changes how people feel about a long drive versus the train.

Worked example: a diesel van for a sole trader

Now picture a self-employed courier running a diesel van at 38 mpg with diesel at £1.45 a litre.

• Cost per gallon = 4.546 × £1.45 = £6.59
• Pence per mile = (£6.59 ÷ 38) × 100 = 17.3p per mile

If a job involves 60 miles of driving, the fuel alone costs about 60 × 17.3p = £10.40. That is the floor for what you should charge before you have covered a single minute of your time. If you claim mileage against your business, the HMRC Approved Mileage Allowance Payments scheme lets you claim a set rate per business mile instead of logging actual fuel and wear; check the current rate on gov.uk and our mileage allowance calculator to see what you can claim back.

From fuel cost to true running cost per mile

Fuel is only part of the story. A running cost per mile calculator-style view spreads every cost of keeping a car on the road across the miles you drive. The wider formula is:

True cost per mile = total annual running costs ÷ annual miles

Total annual running costs typically include fuel, insurance, vehicle excise duty (road tax), servicing and MOT, tyres, breakdown cover, and depreciation, which is usually the biggest hidden cost of all. Here is a realistic build-up for someone driving 10,000 miles a year in the 45 mpg petrol car above:

• Fuel: 10,000 × 14.1p = £1,410
• Insurance: £600
• Vehicle excise duty: £195
• Servicing and MOT: £350
• Tyres (spread over the year): £200
• Depreciation: £1,500

That comes to £4,255 a year. Divide by 10,000 miles and the true cost is about 42.6p per mile — three times the fuel-only figure. This is why per-mile costs from a fleet or business perspective look so much higher than the number at the pump. To plan those bills as a whole, our cost of living calculator and a simple household budget calculator help you slot motoring into your wider monthly spending.

Petrol, diesel or electric: comparing pence per mile

Electric cars change the sum entirely because you measure consumption in miles per kWh, not mpg, and the price you pay swings hugely between cheap overnight home charging and rapid public chargers. The method is the same idea, though: cost per mile = price per kWh ÷ miles per kWh. A car doing 3.5 miles per kWh on a 9p overnight tariff costs about 2.6p a mile, while the same car on a 75p rapid charger costs over 21p a mile. Work yours out with the EV charging cost calculator, and compare petrol or diesel scenarios side by side using our fuel cost calculator.

How to bring your cost per mile down

• Drive for economy. Smooth acceleration, easing off early, and keeping to 60-65 mph on motorways can lift real mpg by 10% or more, which feeds straight into a lower pence per mile.
• Check tyre pressures monthly. Under-inflated tyres add rolling resistance and wear out faster, hitting both fuel and tyre costs.
• Lose the dead weight. Roof bars, boxes and a boot full of clutter all cost mpg. Remove what you are not using.
• Shop the pump price. A few pence a litre across a year of fills adds up. Supermarket forecourts are often cheaper than motorway services.
• Keep a mileage log. If any of your driving is for work, a tidy record lets you claim it properly. A mileage tracker makes that painless at tax time.

Common mistakes to avoid

• Using the brochure mpg. Official figures flatter real economy. Measure your own over a few fills for a number you can trust.
• Mixing up gallons and litres. The UK gallon is 4.546 litres; the US gallon (3.785 litres) gives a wrong answer. This calculator uses UK gallons.
• Forgetting depreciation. The slow drop in your car's value is usually the single largest running cost, yet it never shows up on a receipt.
• Charging a client only the fuel rate. If you drive for work, the fuel figure ignores wear, tyres and your time. Price the whole job, not just the petrol.
• Comparing EV home and public charging as if they were the same. The per-mile gap between a cheap overnight tariff and a rapid charger can be eightfold.

For a fuller picture of the costs of ownership, our car finance calculator shows what monthly repayments add to each mile you drive.

These figures are estimates for guidance only and not personal tax or financial advice. Always confirm current fuel prices, allowances and HMRC mileage rates on gov.uk before relying on them.