True ownership cost is broadly: depreciation + finance interest and fees + insurance + tax + fuel or charging + maintenance and tyres + parking and other running costs. If you sell before the finance ends, the remaining finance balance matters too.
The biggest invisible cost is often depreciation
Depreciation is simply the difference between what you pay for the vehicle and what it is worth later. It does not leave your bank account as a monthly Direct Debit, which is why it is easy to ignore.
Buy a car for £25,000 and sell it four years later for £12,000 and £13,000 of value has disappeared. That £13,000 is an economic cost of ownership even if you bought the car for cash and never paid a penny of interest.
There is no single depreciation rate you should assume. Model, age, mileage, condition, market demand, powertrain and the wider used-car market all matter. That is why the True Cost of Car Ownership Calculator asks you for an expected resale value rather than pretending to know the future.
Finance interest is separate from depreciation
If you borrow to buy the car, you are paying for two things at once: the vehicle's loss in value and the cost of financing the capital. A £20,000 loan over four years at 8.9% APR has a payment of roughly £497 a month before fees. Part repays the amount borrowed and part is interest.
When comparing cars, it helps to separate the finance interest from the capital repayment. Capital is not entirely “lost” because some of it becomes equity in the car. Interest is a financing cost.
The running costs that need their own lines
- Insurance: price the exact car and driver rather than using a generic estimate.
- Vehicle tax: check the current rate for the vehicle. Rules and supplements can change.
- Fuel or electricity: use your own mileage and realistic consumption where possible.
- Servicing and repairs: newer does not mean zero maintenance, and older cars can have more volatile repair bills.
- Tyres: larger wheels and high-performance tyres can materially change the annual budget.
- MOT: include the test where the car requires one, but remember failures and remedial work are separate costs.
- Breakdown cover, parking, permits, tolls and cleaning: individually small costs can become material over several years.
A worked example
Suppose you buy a £25,000 car, use a £5,000 deposit and finance £20,000 for four years at 8.9% APR. You expect the car to be worth £12,000 after four years. Assume £900 a year insurance, £250 vehicle tax, £900 maintenance and tyres, £160 a month fuel, and £60 a month parking and other costs.
The monthly finance payment is only one part of the picture. Over four years the car also loses £13,000 of value and racks up thousands of pounds of insurance, fuel, maintenance and parking. The all-in monthly equivalent can therefore be dramatically higher than the finance quote displayed in an advert.
Why resale equity matters if you change early
If you sell a financed car before the agreement has been repaid, compare the expected resale value with the finance balance that would still be outstanding. If the car is worth £16,000 and the remaining balance is £13,000, you have roughly £3,000 of equity before selling costs. If the balance is £18,000, you have a £2,000 shortfall to settle.
The calculator models this explicitly, which makes it useful for people who tend to change cars every two or three years instead of keeping them until the finance ends.
Do not optimise only for the cheapest car
Lowest total cost is not the only valid objective. Reliability, safety, practicality, accessibility, driving enjoyment and the cost of your time matter. The purpose of a true-cost calculation is not to tell everyone to buy the cheapest possible car. It is to show the price of the trade-off clearly.
Use a range, not one resale forecast
Run the calculator at a stronger and weaker resale value. If the car still fits your finances when resale is lower than hoped, the decision is more resilient. If the economics only work when the car holds an unusually high value, you have found the assumption that needs the most scrutiny.
What to do next
First use the Car Affordability Calculator to set the overall price range. Then use the True Cost of Car Ownership Calculator for the exact vehicle. If you are financing it, compare the agreement separately with the Car Finance Calculator.
Important: Budget Wizard provides educational guides and planning tools, not personalised financial advice. Borrowing, investing and major spending decisions depend on your circumstances. If you are struggling with priority bills or debt, seek free regulated or charitable support before taking on new commitments.
