Most people price a journey on fuel alone, which understates the real figure by a factor of two or three. Insurance, road tax, servicing, tyres and above all depreciation are incurred whether the car moves or not. Spreading them across the miles you actually drive is the only honest way to compare driving with the alternatives.
That split also explains a counter-intuitive result: the more miles you cover, the lower the cost per mile, because the fixed annual costs are shared over more of them. A car doing 4,000 miles a year can easily cost twice as much per mile as the identical car doing 15,000, even though the second one costs far more in total. Every cost figure here is an editable input because insurance premiums, road tax bands and servicing intervals vary by driver, model and region.
A car covering 10,000 miles at 42 mpg burns 1082 litres, which is £1,537 at £1.42 a litre. Adding £620 insurance, £190 road tax, £450 servicing and £1,800 depreciation gives £4,597 a year, or 46.0 pence per mile. Fuel is only 33 per cent of that total.
The formula
fuel cost- Miles ÷ mpg × 4.54609 × price per litre
fixed costs- Insurance, road tax, servicing and depreciation for the year
annual miles- The distance those fixed costs are spread across
× 100- Converts pounds per mile into pence per mile
How to use this calculator
- Enter your annual mileage and choose miles or kilometres.
- Enter your real fuel economy and the pump price you pay.
- Enter insurance, road tax and a yearly figure for servicing, MOT and tyres.
- Add your annual depreciation estimate to see the full pence-per-mile cost.
Worked examples
10,000 miles a year at 42 mpg
Fuel is 1082 litres or £1,537. Fixed costs of £620, £190, £450 and £1,800 total £3,060, so the year costs £4,597 — 46.0p per mile, of which only 15.4p is fuel.
The same car doing 4,000 miles
Fuel falls to £615 but the £3,060 of fixed costs does not move, so the year costs £3,675 — 91.9p per mile. Low mileage makes each mile dramatically more expensive.
How to read your score
Frequently asked questions
Why does driving less make each mile cost more?
Because insurance, road tax, servicing and most of depreciation are annual costs that do not shrink when the car sits still. Halving your mileage roughly doubles the standing cost carried by each mile, even though the total spend falls.
What should I put for depreciation?
Estimate what the car will be worth when you sell it, subtract that from what you paid, and divide by the years you will keep it. A declining-balance projection gives a better year-by-year figure than a straight average, particularly on a car under three years old.
Should I include finance payments?
Not in addition to depreciation, or you will count the same loss twice. If you are on PCP or HP, use either the depreciation figure or the finance interest plus the deposit contribution — but be clear which, and do not add both.
Does this compare fairly against public transport?
For a marginal journey, compare the fuel-only figure, since the standing costs are incurred anyway. For a decision about whether to own a car at all, use the full figure, because that is what actually stops being spent if the car goes.
What about tyres and unexpected repairs?
Fold them into the servicing field as an annual average. A set of four tyres every three years and an allowance for one non-trivial repair are what turn an optimistic servicing figure into a realistic one.
Cost per mile reference
| Annual mileage | Fuel cost | Fuel p/mile | Fixed p/mile | Total p/mile | Year total |
|---|---|---|---|---|---|
| 3,000 miles | £461 | 15.4p | 102.0p | 117.4p | £3,521 |
| 5,000 miles | £769 | 15.4p | 61.2p | 76.6p | £3,829 |
| 8,000 miles | £1,230 | 15.4p | 38.2p | 53.6p | £4,290 |
| 10,000 miles | £1,537 | 15.4p | 30.6p | 46.0p | £4,597 |
| 12,000 miles | £1,844 | 15.4p | 25.5p | 40.9p | £4,904 |
| 15,000 miles | £2,306 | 15.4p | 20.4p | 35.8p | £5,366 |
| 20,000 miles | £3,074 | 15.4p | 15.3p | 30.7p | £6,134 |
| 30,000 miles | £4,611 | 15.4p | 10.2p | 25.6p | £7,671 |
Fuel pence per mile is constant because it scales with distance; the fixed component falls as mileage rises. Replace every cost figure with your own.