What this calculator works out
This calculator multiplies distance by a cost per mile and adds parking and tolls, giving the total cost of a journey.
Everything depends on which cost per mile you use. Fuel alone is around 15p; total running cost including depreciation, insurance and maintenance is around 45p. They answer different questions.
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Before you choose a rate
- For comparing against a train fare on a journey you would make anyway, fuel-only is the honest figure — the car's fixed costs are paid regardless.
- For deciding whether to own a car at all, or for claiming mileage, the full running cost is the right basis.
- HMRC's approved mileage rate is 45p a mile for the first 10,000 business miles in a car, then 25p. That rate is intended to cover all running costs.
- Add parking and tolls separately. They are frequently the largest single item on an urban journey.
A car doing 45 mpg at £1.45 a litre costs about 14.7p a mile in fuel. HMRC's 45p reflects depreciation, insurance, tax, servicing, tyres and repairs alongside it. Comparing a car journey against public transport on fuel alone understates the car by roughly three times — but including fixed costs on a journey you would make anyway overstates it.
How this calculator works
Distance times rate, plus extras:
Total = distance in miles × cost per mile in pence ÷ 100 + parking and tollsThe calculation is deliberately simple so that the rate can carry whatever assumption you choose. Running it twice — once at a fuel-only rate and once at a full running-cost rate — brackets the answer more usefully than a single figure.
Worked example: a hundred miles
Using the default figures — 100 miles at 45p a mile plus £5 of parking:
- Mileage cost: £45.00
- Total: £50.00
Now run it at a fuel-only rate of 14.7p: the same journey costs £14.70 plus £5, or £19.70. Against a £35 train fare, the car looks expensive on one basis and cheap on the other, and both figures are correct. The question being asked determines which applies — and quoting the convenient one is how these comparisons usually go wrong.
Common mistakes
- Using fuel-only cost to justify car ownership. Fixed costs are most of the total.
- Using the full rate for a journey you would make anyway. It overstates the marginal cost.
- Forgetting parking and tolls. On urban journeys they frequently exceed the fuel.
- Comparing a single-occupancy fare against a whole car. Cars carry passengers at no extra cost.
- Ignoring the time cost. A train journey that can be worked is not equivalent to driving.
Frequently asked questions
What is HMRC's mileage rate for?
It is the amount an employer can reimburse for business use of a personal car without it counting as taxable pay — 45p a mile for the first 10,000 miles in a tax year and 25p thereafter, for cars and vans. It is intended to cover all running costs including depreciation. Where an employer pays less, the difference can generally be claimed as tax relief.
What does a car actually cost per mile?
It varies enormously with the car, the mileage and how long it is kept. Depreciation is usually the largest single component and falls per mile as annual mileage rises, since it is largely time-based. A car doing 5,000 miles a year costs far more per mile than the same car doing 15,000, which is why low-mileage ownership is disproportionately expensive.
Should I include depreciation on a specific journey?
For a marginal decision, no — the car depreciates whether or not you make the trip, and only the additional wear attributable to the miles is genuinely caused by it. For a decision about whether to own the car, yes, because then the whole cost is in question.
How do I compare fairly with public transport?
Use the marginal cost of driving — fuel, parking, tolls and any additional wear — against the full fare, and count everyone travelling. Then consider the time and what can be done with it. A car carrying four people is usually cheaper than four fares; one person driving to a city centre frequently is not.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — HMRC approved mileage rates and vehicle running cost guidance
- MoneyHelper — the true cost of running a car
Sources are checked at publication and can change — how I choose and check references.