How we value a car

The source is BidBetter's own auction sales database: completed results from 19 auction houses, 302,360 sold lots from 1 January 2016 to 1 November 2026. Only rows cleared for publication are read; anything else is excluded before any statistic is computed.

Each model page is restricted to one make, one model string (or the several strings a generation is stored under) and a year window. The window is chosen to match the generation, not to flatter the median: where a generation has no string of its own in the data, the year range does the work.

Rules run in this order. The first four remove rows that are not sales or not prices; the fifth and sixth remove rows that are not the car; the last three remove rows that cannot be a price for this car. Across the 28 models on this site, 4,342 of 32,418 pulled rows were removed, leaving 28,076.

Two of these rules are worth calling out because they changed published figures. The replica rule was added after measuring the Porsche 356: leaving replicas in published a median of $99,999 for a car that really sells at $118,000. The ceiling rule is asymmetric on purpose — a $4,295,000 1976 Porsche 935 is a real sale of a real car, so it is held out of the median and disclosed rather than deleted.

The median is the 50th percentile of the cleaned sale prices. The typical range is the 25th to 75th percentile: half of all sales fall inside it. Percentiles are linearly interpolated on the sorted prices, which is the same calculation PostgreSQL's percentile_cont performs, so a figure can be reproduced straight from SQL.

A model publishes a median only at 20 or more cleaned sales, and nothing publishes below five. Below 20 the page would be describing a handful of cars rather than a market.

Each page also shows the full observed range, the cheapest and dearest sale that survived cleaning. That range is set by outliers, so it is a boundary rather than a guide to what most cars bring.

Dollars only. Sales in other currencies are excluded. On some models that is a large share of the market — the Porsche 964, the Mercedes 190SL and the BMW E30 M3 trade heavily in Britain and Europe — so a dollar median is a median of the dollar sales, which is a narrower claim than "what the car is worth".

Model and year, not car. A page describes a model. It does not know about this car's engine, paint, paperwork or accident history, and no model-level figure can.

Mileage is not used to adjust. Only 6.6% of these sales carry an odometer reading with a unit attached. Where it is recorded it tracks price clearly (see mileage and value), but it cannot be applied to the other 93% without inventing a number.

Not an appraisal. This is a description of a market, not an inspection of a car, and it does not predict an auction result. See the disclaimer.

A model's median can be recomputed from the published sales without trusting this page: take the model's sales table, drop anything not sold in dollars, sort the prices and take the middle value. The page lists its most recent 15 sales with a link to each auction record, the model-year split, the body-style split and the transmission split, so the arithmetic is checkable against the record.

The dataset behind all of it is described on the dataset page, and the question pages are indexed from model values.