Why Zillow Is Often Wrong

"Morgan, Zillow says my house is worth $825,000. Is that accurate?"

I get some version of that question more than almost any other. The honest answer is always the same: maybe, but probably not exactly — and the gap between "maybe" and "exactly" matters more than most people realize, because that number is about to inform one of the biggest financial decisions of your life.

Homeowners don't actually want to know what Zillow thinks. They want to know what their house is really worth. The Zestimate is just the easiest place to start looking for that answer. It isn't the same thing as finding it.

Zestimates Are a Computer's Best Guess, Not a Professional's Opinion

Zillow's Zestimate comes from an algorithm. It pulls public records, recent sales, tax assessments, and whatever data it can scrape together, then runs it through a formula to spit out a number. That's it. There's no person driving by your house. There's no one walking through your kitchen. There's no human oversight checking whether that number actually makes sense for your specific property.

I've been selling real estate in Austin since 2009. Pricing a home well is not just plugging numbers into a spreadsheet. It's part science and part art. You have to understand the block, the school zone, what buyers are actually responding to right now, and what makes one house different from the one three doors down. A computer doesn't know any of that.

Zillow Doesn't Know What Your House Actually Looks Like

Here's the big one. Zillow's Zestimate is built almost entirely off public record data — permits, tax filings, square footage on file, past sale prices. What it doesn't have is any real sense of your home's current condition.

Did you just gut renovate the kitchen? Zillow probably has no idea. Is there foundation work that never got permitted? Zillow won't catch that either. Is the flooring original from 1987 and the whole place needs updating? The algorithm has no way to know, because nobody told it to look.

Picture two homes on the same street: same floor plan, same square footage, built the same year. On paper, to an algorithm, they're identical. In person, they're not close. One has a renovated kitchen and sits on a quiet interior lot. The other still has its original finishes and backs up to a busy road that buyers notice the second they pull into the driveway. Same square footage, same bedroom count, meaningfully different homes. Zillow sees the same address data for both. I see the difference in about ninety seconds of walking through the front door.

A home's value isn't just square footage and bedroom count. It's condition, finishes, layout, natural light, how the home feels when you walk in the door. None of that shows up in public records, so none of it shows up in a Zestimate.

So What Should You Actually Trust?

Not a number generated by an algorithm that's never set foot in your home. A real comparative market analysis, done by someone who knows your neighborhood, has seen your property in person, and understands what's actually happening in the Austin market right now — not six months ago, when the last data update ran.

This is exactly why I built my whole brand around being the agent who tells the truth. I'm not going to hand you an inflated number to make you feel good, and I'm not going to lowball you to make a quick sale either. I'm going to walk your property, look at comparable sales that actually compare, and give you a real number based on real market knowledge.

My job was never to out-guess Zillow. My job is to tell you what Zillow can't: what your home is actually worth, based on what's actually true about it. If your home is worth more than the Zestimate, I'll tell you, and I'll show you the comparables that prove it. If it's worth less, I'll tell you that too, even though that's the harder conversation to have. Either way, you'll know the real number before you make a decision this size, not after.

Written by Morgan Simpson, founder of Simpson Realty Group — more about Morgan.