The Zestimate is the first number most people look at when they think about selling. It’s on Zillow’s homepage, it’s confident, it’s precise to the dollar, and it’s often wrong. Not catastrophically wrong, usually — but wrong by enough that pricing your home off it can cost you tens of thousands of dollars or weeks on the market. Here’s why, and what real pricing looks like.
A Zestimate is the output of an algorithm. It pulls public records (square footage, lot size, year built), tax assessments, and sales history from a wide radius, then runs a regression to spit out a number. Zillow itself publishes its median error rate — around 2.4% nationally for on-market homes, and roughly 7–9% for off-market ones. On a $400,000 Wisconsin home, that 7% miss is $28,000. That’s the difference between a clean sale and a stalled listing.
A comparative market analysis — a CMA — is what an actual REALTOR® prepares. It starts with the same public data the algorithm uses, but then it does the work the algorithm can’t. It looks at three to six recently sold comparable homes (within roughly half a mile, similar square footage, similar age, similar style), evaluates each one’s condition based on MLS photos and — ideally — personal walk-throughs, and adjusts up or down for differences: an updated kitchen, a finished basement, a busy road, a north-facing backyard.
The algorithm doesn’t know that the comp two streets over had a brand-new roof and a finished walkout the seller spent $40,000 on. It doesn’t know that the house across the cul-de-sac has a leaky basement that knocked $15,000 off its sale price during inspection negotiations. It doesn’t know your neighborhood is currently white-hot because the local elementary school just got a new principal everyone loves. A real agent does. That’s the difference.
There’s also the matter of pending sales and active listings. The Zestimate is backwards-looking. A CMA looks at what’s under contract right now — because today’s pending sales become tomorrow’s closed comps — and it looks at what’s currently competing with you on the market. If three similar homes just listed at $410,000 last week and yours goes up at $435,000, the algorithm doesn’t care. The buyers do.
The pricing strategy itself is the other half. A CMA isn’t just a number, it’s a recommendation. Should you list at the comp number to get multiple offers? List slightly above to leave negotiation room? List below to drive a frenzy? The right call depends on inventory, season, your timeline, and your tolerance for risk. The algorithm gives you a number. A good agent gives you a strategy.
I’ve had sellers come to me convinced their home was worth what the Zestimate said — sometimes high, sometimes low. About eight times out of ten, the CMA lands within $10,000 of the Zestimate, and the algorithm gets a small win. The other two times? The CMA was off by $25,000 to $80,000, and listing at the algorithm’s number would have left real money on the table or kept the home sitting for months.
If you’re thinking about selling — even if it’s not for another year — ask for a CMA. They’re free, they take about a day to prepare, and even if you decide to wait, you’ll have a real number to plan around instead of a guess dressed up in a confidence interval. The Zestimate is fine for curiosity. A CMA is what you use to make decisions.
