How this estimate is built
The calculation applies a declining-balance depreciation curve, commonly used across UK valuation guides: roughly 25% lost in year one, 15% in year two, 12% in year three, then 8% a year through years four to six, 5% a year through years seven to ten, and 3% a year beyond that. This reflects the well-documented pattern that depreciation is steepest when a car is newest and flattens significantly with age.
Mileage adjusts the estimate slightly: a car with meaningfully higher mileage than the roughly 10,000 miles/year UK average for its age is nudged down, and a genuinely low-mileage example is nudged up, within a modest range, since mileage is a real factor but not one this tool can weigh anywhere near as precisely as an actual valuation database would.
What this doesn't account for at all: the specific make and model's own resale reputation (some cars hold value far better or worse than the average), condition, service history, colour, optional extras, or current local market demand, all of which can easily move a real car's value well outside this rough range.
Frequently asked questions
Is this an accurate car valuation?
No. There is no free, publicly available UK car valuation data source, so this tool applies a typical industry-wide depreciation curve to the original price, age, and mileage instead. It gives a rough ballpark, not a figure to price a sale or purchase against.
How much does a car actually depreciate in the UK?
Typically 15 to 25 percent in the first year, reaching 40 to 60 percent lost by three years old, then slowing to around 5 to 8 percent a year through mid-life, and 3 to 5 percent a year once a car passes 8 to 10 years old.