How UnderSticker works
How the deal rating works
Every listing gets a rating by comparing its asking price to an estimated fair market price. We build that estimate in four steps:
- Estimate a fair price. A gradient-boosted machine-learning model trained on every current listing predicts a typical price from the car’s model, trim, age, mileage, body style and region.
- Anchor to peers. For models with a huge price spread (think a base trim sharing a badge with a $400k halo car), we pull the estimate toward the median of the car’s own trim peers, so a base car isn’t priced like the flagship.
- Discount for history. Cars with reported accidents, or rebuilt/salvage titles, are worth less than a clean equivalent, so we apply a condition discount to the fair price.
- Gate on confidence. If the estimate is too uncertain for a given car, we leave it unrated instead of guessing.
The asking price is then compared to that fair price:
Data & freshness
Listings are aggregated from Cars.com, CarGurus and Autotrader (with eBay Motors being added) and the same car is merged across sites by VIN. Inventory refreshes weekly, and you can request any model on demand. Prices shown are the dealers’ advertised list prices.
FAQ
Where does the data come from?
We aggregate live listings from Cars.com, CarGurus and Autotrader (with eBay Motors being added), deduplicate the same car across sites by VIN, and refresh weekly. Prices are the dealers’ advertised list prices.
What does “fair price” mean?
It’s our model’s estimate of a typical asking price for a car with the same model, trim, age, mileage, body style and region — not an appraisal or an offer. A listing far under its fair price is flagged as a deal.
Why is a listing left unrated?
When the model isn’t confident in a car’s fair price (the estimate lands more than 25% away from the ask, which usually means a rare trim or a data quirk), we show no rating rather than a number we don’t trust.
Can I track a car that isn’t listed?
Yes — search any make and model on the home page. If we don’t track it yet, we’ll fetch it on demand.
How accurate is the model?
On current inventory it explains roughly 94% of price variation and lands within about 6% of the asking price on a typical car. It’s a guide, not gospel — always verify a specific car yourself.
Important
UnderSticker is an independent research tool and is not affiliated with Cars.com, CarGurus, Autotrader, eBay, or any manufacturer or dealer. Prices are advertised list prices, not offers, and may exclude fees. Deal ratings are model estimates and can be wrong — they are informational only and are not financial, purchase, or appraisal advice. Always confirm a vehicle’s history (e.g. via CARFAX) and condition before buying.