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.

Metropolitan Area 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
Atlanta-Sandy Springs-Marietta, GA MSA 99% 99% 25% 44% 65% 12.1%
Baltimore-Towson, MD MSA 99% 99% 29% 50% 73% 10.0%
Boston-Cambridge-Quincy, MA-NH MSA 95% 95% 27% 47% 71% 10.9%
Chicago-Naperville-Joliet, IL-IN-WI MSA 99% 94% 29% 51% 75% 9.7%
Cincinnati-Middletown, OH-KY-IN MSA 93% 88% 29% 50% 72% 10.1%
Cleveland-Elyria-Mentor, OH MSA 99% 99% 24% 44% 68% 11.6%
Dallas-Fort Worth-Arlington, TX MSA 99% 99% 15% 27% 39% 34.2%
Denver-Aurora, CO MSA 99% 99% 30% 51% 73% 9.8%
Detroit-Warren-Livonia, MI MSA 87% 82% 16% 30% 51% 19.6%
Houston-Baytown-Sugar Land, TX MSA 99% 99% 22% 40% 63% 13.6%
Kansas City, MO-KS MSA 91% 53% 16% 32% 53% 18.3%
Los Angeles-Long Beach-Santa Ana, CA MSA 88% 88% 30% 52% 78% 9.4%
Miami-Fort Lauderdale-Miami Beach, FL MSA 99% 99% 18% 33% 56% 16.6%
Minneapolis-St. Paul-Bloomington, MN-WI MSA 99% 99% 26% 47% 70% 10.9%
New York-Northern New Jersey-Long Island, NY-NJ-PA MSA 99% 99% 25% 44% 69% 11.7%
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD MSA 99% 99% 30% 51% 73% 9.7%
Phoenix-Mesa-Scottsdale, AZ MSA 99% 99% 26% 47% 73% 10.6%
Pittsburgh, PA MSA 87% 80% 21% 39% 64% 13.6%
Portland-Vancouver-Beaverton, OR-WA MSA 99% 99% 30% 53% 78% 9.0%
Providence-New Bedford-Fall River, RI-MA MSA 99% 99% 21% 40% 64% 13.4%
Riverside-San Bernardino-Ontario, CA MSA 99% 99% 22% 41% 67% 12.9%
Sacramento-Arden-Arcade-Roseville, CA MSA 99% 99% 26% 47% 71% 10.8%
San Diego-Carlsbad-San Marcos, CA MSA 94% 93% 30% 52% 77% 9.5%
San Francisco-Oakland-Fremont, CA MSA 91% 91% 29% 52% 75% 9.4%
San Jose-Sunnyvale-Santa Clara, CA MSA 86% 86% 37% 60% 81% 7.6%
Seattle-Tacoma-Bellevue, WA MSA 99% 99% 33% 57% 80% 8.2%
St. Louis, MO-IL MSA 98% 93% 24% 44% 69% 11.8%
Tampa-St. Petersburg-Clearwater, FL MSA 99% 99% 21% 39% 63% 13.7%
Virginia Beach-Norfolk-Newport News, VA-NC MSA 95% 45% 31% 52% 70% 9.4%
Washington-Arlington-Alexandria, DC-VA-MD-WV MSA 95% 91% 32% 54% 77% 8.9%
State 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
Alaska 72% 44% 27% 48% 73% 10.7%
Alabama 68% 18% 15% 29% 46% 22.6%
Arkansas 74% 30% 31% 52% 72% 9.3%
Arizona 99% 99% 25% 47% 72% 10.9%
California 99% 97% 27% 48% 73% 10.4%
Colorado 99% 97% 31% 52% 75% 9.4%
Connecticut 99% 99% 30% 54% 77% 9.1%
District of Columbia 99% 99% 28% 50% 72% 10.0%
Delaware 99% 66% 21% 37% 54% 16.8%
Florida 99% 99% 20% 36% 59% 15.2%
Georgia 99% 69% 24% 44% 64% 12.3%
Hawaii 99% 88% 27% 48% 70% 10.6%
Iowa 55% 18% 30% 52% 73% 9.5%
Idaho 55% 43% 14% 29% 55% 17.7%
Illinois 83% 74% 29% 51% 76% 9.6%
Indiana 51% 33% 9% 17% 35% 29.3%
Kansas 70% 2% 17% 30% 46% 21.7%
Kentucky 36% 22% 24% 41% 61% 13.2%
Louisiana 52% 22% 20% 36% 57% 16.1%
Massachusetts 99% 99% 26% 46% 70% 11.0%
Maryland 99% 98% 29% 50% 73% 10.0%
Maine 0% 0% -- -- -- --
Michigan 89% 73% 16% 31% 52% 18.6%
Minnesota 74% 70% 25% 45% 68% 11.4%
Missouri 65% 55% 22% 41% 65% 13.1%
Mississippi 41% 0% -- -- -- --
Montana 78% 43% 17% 35% 58% 15.5%
North Carolina 99% 80% 30% 51% 72% 9.6%
North Dakota 34% 9% 20% 38% 61% 14.7%
Nebraska 50% 23% 36% 60% 82% 7.5%
New Hampshire 18% 16% 23% 36% 54% 18.0%
New Jersey 99% 79% 25% 44% 68% 11.8%
New Mexico 63% 54% 19% 36% 58% 16.2%
Nevada 99% 99% 21% 39% 65% 13.5%
New York 99% 99% 23% 41% 64% 13.0%
Ohio 89% 76% 27% 48% 70% 10.7%
Oklahoma 71% 59% 34% 56% 75% 8.1%
Oregon 99% 94% 27% 50% 73% 10.1%
Pennsylvania 84% 67% 28% 49% 72% 10.2%
Rhode Island 99% 99% 20% 39% 63% 14.0%
South Carolina 99% 94% 28% 48% 69% 10.6%
South Dakota 0% 0% -- -- -- --
Tennessee 99% 84% 25% 43% 65% 12.3%
Texas 99% 82% 16% 29% 45% 24.5%
Utah 99% 93% 20% 37% 61% 14.8%
Virginia 78% 61% 34% 56% 76% 8.4%
Vermont 59% 0% -- -- -- --
Washington 99% 99% 30% 52% 75% 9.4%
Wisconsin 83% 37% 27% 47% 71% 10.7%
West Virginia 99% 18% 15% 29% 51% 19.3%
Wyoming 38% 35% 21% 37% 59% 16.1%
Region 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
All 50 States 88% 74% 25% 44% 67% 11.8%

Last updated: May 20, 2009
* Click on a state to see detailed county data (accuracy based only on counties for which we have data)
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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