Our methodology
We would rather show our working than ask you to trust a black box. Here is exactly how every figure on this site is produced.
The principle
A used car's value is driven overwhelmingly by four things: its price when new, its vehicle type, its age and mileage, and its condition. Our estimator combines these with a transparent declining-balance depreciation model. It is intentionally market-neutral — it uses no licensed price book, which is what lets it work in any country and any currency. The trade-off is honesty: it produces a realistic range, not a guaranteed sale price.
Depreciation by vehicle type
Each vehicle type loses value on its own curve. The first year always falls hardest; later years follow a gentler annual rate. The figures we use:
| Vehicle type | First-year drop | Each later year | Typical miles/year |
|---|---|---|---|
| Economy / compact | 20% | 13% | 12,000 |
| Mid-size sedan | 22% | 14% | 12,000 |
| SUV / crossover | 21% | 13% | 13,000 |
| Pickup truck | 18% | 11% | 14,000 |
| Minivan / MPV | 23% | 14% | 13,000 |
| Luxury | 28% | 18% | 10,000 |
| Sports / performance | 20% | 12% | 8,000 |
| Electric (EV) | 30% | 17% | 11,000 |
Retained value for a given age is the first-year retention multiplied by each subsequent year's retention. For example, a mid-size sedan at five years old retains roughly 0.78 × 0.86⁴ ≈ 43% of its original price, before mileage and condition adjustments. Plotted, the model produces this curve — steep first year, gentler thereafter:
Mileage adjustment
We compare the odometer to the distance a car of that type and age would typically have covered. The value is then adjusted by 0.18% for every 1,000 miles above or below that expected figure, capped at ±25% so extreme inputs stay sensible. A car driven less than average is worth more; a high-mileage example is worth less.
Condition factors
| Condition | Adjustment |
|---|---|
| Excellent | +5% |
| Good | +0% |
| Fair | -12% |
| Poor | -28% |
The final estimate is: original price × retained value × mileage factor × condition factor. We present it as a range of roughly ±8% around that point, because real sales always vary with local demand, timing, colour and history.
Finance calculations
Loan payments use the standard amortising-loan formula: the amount financed is spread over the term at the stated APR, with each payment covering interest first. Affordability runs that formula in reverse — from a monthly payment to a maximum price. Lease-versus-buy compares net cash spent over the same term, crediting the car's resale value to the buying option.
What this is not
These tools give estimates for general guidance only. They are not a formal appraisal, an offer to buy, or financial advice. For a binding figure, get an in-person inspection from a dealer or independent appraiser, and confirm finance terms with a regulated lender.
Keeping it current
Depreciation behaviour shifts over time — EVs are a fast-moving example. We review these assumptions periodically and update this page when the model changes, so what you read here always matches what the calculators do.