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	Three Stars	99%	99%	26%	46%	68%	11.2%
Baltimore-Towson, MD MSA	Four Stars	99%	99%	31%	51%	72%	9.6%
Boston-Cambridge-Quincy, MA-NH MSA	Three Stars	95%	95%	26%	49%	74%	10.3%
Chicago-Naperville-Joliet, IL-IN-WI MSA	Four Stars	99%	94%	30%	52%	77%	9.3%
Cincinnati-Middletown, OH-KY-IN MSA	Three Stars	93%	88%	29%	49%	73%	10.1%
Cleveland-Elyria-Mentor, OH MSA	Two Stars	99%	99%	25%	45%	69%	11.5%
Dallas-Fort Worth-Arlington, TX MSA	Four Stars	99%	99%	30%	52%	74%	9.4%
Denver-Aurora, CO MSA	Three Stars	99%	99%	29%	50%	74%	9.9%
Detroit-Warren-Livonia, MI MSA	Two Stars	87%	82%	20%	38%	61%	14.4%
Houston-Baytown-Sugar Land, TX MSA	Two Stars	99%	99%	25%	45%	68%	11.7%
Kansas City, MO-KS MSA	Two Stars	91%	53%	24%	43%	66%	12.3%
Los Angeles-Long Beach-Santa Ana, CA MSA	Three Stars	88%	88%	27%	50%	77%	10.1%
Miami-Fort Lauderdale-Miami Beach, FL MSA	Two Stars	99%	99%	24%	44%	70%	11.8%
Minneapolis-St. Paul-Bloomington, MN-WI MSA	Four Stars	99%	99%	31%	54%	78%	8.9%
New York-Northern New Jersey-Long Island, NY-NJ-PA MSA	Two Stars	99%	99%	26%	46%	70%	11.3%
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD MSA	Four Stars	99%	99%	29%	52%	74%	9.4%
Phoenix-Mesa-Scottsdale, AZ MSA	Three Stars	99%	99%	29%	51%	77%	9.7%
Pittsburgh, PA MSA	Two Stars	87%	80%	18%	35%	59%	15.7%
Portland-Vancouver-Beaverton, OR-WA MSA	Four Stars	99%	99%	35%	59%	82%	7.9%
Providence-New Bedford-Fall River, RI-MA MSA	Three Stars	99%	99%	26%	47%	71%	10.6%
Riverside-San Bernardino-Ontario, CA MSA	Two Stars	99%	99%	21%	40%	68%	12.9%
Sacramento-Arden-Arcade-Roseville, CA MSA	Two Stars	99%	99%	24%	45%	72%	11.5%
San Diego-Carlsbad-San Marcos, CA MSA	Three Stars	94%	93%	28%	51%	78%	9.7%
San Francisco-Oakland-Fremont, CA MSA	Four Stars	91%	91%	30%	51%	78%	9.6%
San Jose-Sunnyvale-Santa Clara, CA MSA	Four Stars	86%	86%	41%	64%	87%	6.7%
Seattle-Tacoma-Bellevue, WA MSA	Four Stars	99%	99%	36%	60%	83%	7.5%
St. Louis, MO-IL MSA	Two Stars	98%	93%	24%	45%	70%	11.4%
Tampa-St. Petersburg-Clearwater, FL MSA	Three Stars	99%	99%	24%	46%	70%	11.2%
Virginia Beach-Norfolk-Newport News, VA-NC MSA	Four Stars	95%	45%	39%	60%	77%	7.3%
Washington-Arlington-Alexandria, DC-VA-MD-WV MSA	Four Stars	95%	91%	34%	57%	80%	8.3%

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	Two Stars	70%	44%	25%	45%	68%	11.9%
Alabama	Two Stars	64%	18%	16%	33%	52%	18.8%
Arkansas	Four Stars	68%	30%	30%	54%	77%	9.1%
Arizona	Three Stars	99%	99%	27%	49%	74%	10.2%
California	Three Stars	99%	97%	26%	47%	73%	10.9%
Colorado	Four Stars	99%	97%	31%	53%	76%	9.1%
Connecticut	Four Stars	99%	99%	31%	53%	77%	9.1%
District of Columbia	Two Stars	99%	99%	21%	38%	59%	14.8%
Delaware	Four Stars	98%	66%	34%	56%	76%	8.1%
Florida	Two Stars	99%	99%	23%	43%	67%	12.3%
Georgia	Two Stars	99%	69%	26%	45%	67%	11.4%
Hawaii	Two Stars	95%	88%	23%	46%	74%	11.1%
Iowa	Four Stars	53%	18%	33%	57%	78%	8.1%
Idaho	Two Stars	52%	43%	22%	45%	65%	11.6%
Illinois	Four Stars	81%	74%	30%	51%	76%	9.5%
Indiana	Two Stars	48%	33%	19%	37%	64%	14.2%
Kansas	Two Stars	68%	2%	17%	35%	69%	13.3%
Kentucky	Two Stars	34%	22%	26%	46%	68%	11.5%
Louisiana	Two Stars	49%	22%	18%	33%	52%	18.3%
Massachusetts	Three Stars	99%	99%	26%	48%	73%	10.4%
Maryland	Four Stars	99%	98%	31%	53%	74%	9.2%
Maine	--	0%	0%	--	--	--	--
Michigan	Two Stars	79%	73%	19%	37%	60%	14.9%
Minnesota	Four Stars	71%	70%	31%	53%	77%	9.2%
Missouri	Two Stars	63%	55%	25%	45%	69%	11.5%
Mississippi	One Stars	40%	0%	--	--	--	--
Montana	Two Stars	78%	43%	20%	41%	66%	13.3%
North Carolina	Four Stars	99%	80%	33%	54%	74%	8.8%
North Dakota	One Stars	32%	0%	--	--	--	--
Nebraska	Four Stars	49%	23%	35%	59%	81%	7.6%
New Hampshire	Two Stars	18%	16%	29%	45%	67%	11.6%
New Jersey	Three Stars	99%	79%	29%	50%	76%	9.9%
New Mexico	Two Stars	61%	54%	19%	36%	62%	14.7%
Nevada	Four Stars	99%	99%	28%	52%	79%	9.5%
New York	Two Stars	99%	99%	24%	43%	66%	12.1%
Ohio	Two Stars	87%	76%	26%	46%	69%	11.1%
Oklahoma	Four Stars	69%	59%	32%	52%	71%	9.4%
Oregon	Four Stars	99%	94%	32%	54%	77%	8.9%
Pennsylvania	Three Stars	83%	67%	26%	47%	70%	10.8%
Rhode Island	Two Stars	99%	99%	25%	46%	70%	11.1%
South Carolina	Two Stars	99%	94%	25%	45%	66%	11.8%
South Dakota	--	0%	0%	--	--	--	--
Tennessee	Two Stars	99%	84%	24%	42%	62%	13.0%
Texas	Three Stars	99%	82%	27%	48%	70%	10.7%
Utah	Two Stars	99%	93%	23%	41%	65%	12.9%
Virginia	Four Stars	77%	61%	35%	58%	79%	8.1%
Vermont	One Stars	52%	0%	--	--	--	--
Washington	Four Stars	99%	99%	33%	57%	80%	8.2%
Wisconsin	Four Stars	77%	37%	29%	52%	77%	9.4%
West Virginia	Two Stars	99%	18%	17%	36%	61%	15.1%
Wyoming	Two Stars	37%	35%	22%	42%	68%	12.2%

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	Three Stars	88%	74%	27%	48%	71%	10.6%

Last updated: June 4, 2008
* 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 Dec. 31, 2007.

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:

= Best Zestimate
= Good Zestimate
= Fair Zestimate
= Tax assessor's value, or unable to compute Zestimate accuracy
0 stars = No valuation

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, 35% 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 7.5% of the selling price, and half are off by more than 7.5%.

Zestimates & Comps