Data Coverage and Zestimate® Accuracy

The home data we have compiled to generate a Zestimate home valuation varies by location. Some counties provide all the data we could hope for, but others are lacking such key things as the number of bedrooms and bathrooms, or, in some cases, the square footage of the home. The more data we have, the more accurate the Zestimate. And, we've made it easier for our users to help us improve accuracy by incorporating edited home facts into our Zestimate calculations. In some areas, we might not be able to produce a Zestimate at all, but we do have some basic information on the homes. The tables below show you where we have Zestimates and other home information.

To measure the accuracy of the Zestimates, we've gone back in time and compared the historic Zestimates with the actual transaction prices of homes that sold. The tables below also provide various measures of that accuracy.

What's a Zestimate?

A Zestimate home valuation is Zillow's estimated market value. It is not an appraisal. Use it as a starting point to determine a home's value. Learn more.

  • Texas Counties

Texas

County Zestimate Accuracy % Homes on Zillow % Homes With Zestimates Within 5% of Sale price Within 10% of Sale Price Within 20% of Sale Price Median Error
Angelina 68% 0% -- -- -- --
Bell 99% 0% -- -- -- --
Bexar 99% 99% 15% 31% 48% 21.3%
Brazoria 99% 99% 25% 43% 66% 12.5%
Brazos 99% 99% 22% 42% 66% 12.6%
Caldwell 97% 0% -- -- -- --
Cameron 99% 0% -- -- -- --
Chambers 99% 0% -- -- -- --
Collin 99% 99% 20% 34% 48% 22.4%
Comal 99% 99% 19% 33% 52% 19.0%
Coryell 99% 0% -- -- -- --
Dallas 99% 99% 8% 16% 25% 65.2%
Denton 99% 99% 4% 7% 15% 58.2%
Dimmit 76% 0% -- -- -- --
Ector 99% 0% -- -- -- --
Ellis 99% 99% 4% 8% 18% 47.4%
El Paso 99% 99% 22% 36% 59% 15.0%
Fort Bend 99% 99% 21% 40% 63% 13.3%
Galveston 99% 99% 22% 38% 62% 13.5%
Grayson 99% 99% 3% 8% 16% 74.8%
Gregg 99% 0% -- -- -- --
Guadalupe 99% 99% 26% 42% 57% 13.7%
Hardin 99% 0% -- -- -- --
Harris 99% 99% 22% 40% 63% 13.6%
Harrison 99% 0% -- -- -- --
Hays 99% 99% 5% 9% 20% 47.2%
Henderson 99% 0% -- -- -- --
Hidalgo 99% 0% -- -- -- --
Hood 99% 0% -- -- -- --
Hunt 96% 0% -- -- -- --
Jefferson 99% 99% 11% 27% 49% 21.1%
Johnson 99% 99% 3% 9% 18% 56.4%
Kaufman 99% 99% 6% 11% 21% 57.7%
Kendall 99% 99% 8% 17% 34% 38.0%
Lamar 79% 0% -- -- -- --
Liberty 99% 0% -- -- -- --
Lubbock 99% 99% 4% 7% 15% 75.1%
McLennan 99% 99% 5% 10% 23% 41.1%
Maverick 97% 0% -- -- -- --
Midland 99% 99% 18% 39% 67% 13.2%
Montgomery 99% 99% 20% 38% 64% 13.8%
Nueces 99% 99% 20% 36% 58% 15.4%
Orange 99% 0% -- -- -- --
Parker 99% 99% 10% 21% 32% 36.3%
Potter 99% 0% -- -- -- --
Randall 99% 99% 29% 47% 69% 10.6%
Rockwall 99% 99% 8% 19% 30% 36.8%
San Patricio 99% 0% -- -- -- --
Smith 99% 0% -- -- -- --
Tarrant 99% 99% 28% 46% 65% 11.4%
Taylor 99% 0% -- -- -- --
Tom Green 99% 0% -- -- -- --
Travis 99% 99% 5% 9% 16% 60.0%
Van Zandt 69% 0% -- -- -- --
Victoria 96% 0% -- -- -- --
Waller 99% 0% -- -- -- --
Webb 99% 0% -- -- -- --
Wichita 95% 0% -- -- -- --
Williamson 99% 99% 7% 11% 22% 46.7%
Wilson 99% 0% -- -- -- --
Wise 99% 0% -- -- -- --
Zapata 99% 0% -- -- -- --

Last updated: May 20, 2009
Note: Zestimate accuracy is computed by comparing the final sale price to the Zestimate on or before the sale date. The data herein is computed for the three-month period ending September 30, 2008.

Click here to download an Excel spreadsheet of this data.

Definitions

Zestimate Accuracy/Star Rating:
This rating is tied to the Median Error in an area.
The ratings are as follows:
  • Four Stars = Best Zestimate
  • Three Stars = Good Zestimate
  • Two Stars = Fair Zestimate
  • One Star = Tax assessor's value, or unable to compute Zestimate accuracy
  • 0 stars = No valuation
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Tax Assessor's Value

Depending on the jurisdiction where you live, this value could be the tax assessed, tax appraised, or market assessed value. This value comes from the taxing authority of the city, county or state where you live; this is not Zillow's value.

Note: Tax assessor's values differ from Zillow's Zestimate, which is computed by entering numerous data points into a proprietary formula, often resulting in a more accurate value estimate.

Homes on Zillow:
This indicates the percentage of homes for which we have data (e.g., number of bedrooms or bathrooms) in a particular locale. These are the homes you can find via maps or search on Zillow.com.
Homes With Zestimates:
We can only calculate Zestimates for homes where we have certain data, including transactions. This column indicates the percentage of homes in an area with Zestimates.
Within 5% of Sale Price:
This is the percentage of transactions in a location for which the Zestimate was within 5% of the transaction price. For example, in the Portland area, 30% of the time the Zestimate was within 5% of the selling price.
Within 10% of Sale Price:
This is the percentage of transactions in a location for which the Zestimate was within 10% of the transaction price.
Within 20% of Sale Price:
This is the percentage of transactions in a location for which the Zestimate was within 20% of the transaction price.
Median Error:
Half of the Zestimates in an area were closer than the error percentage and half were farther off. For example, in Seattle, Zestimates for half of the homes are within 8.2% of the selling price, and half are off by more than 8.2%.
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