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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.
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.
| 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 |
|---|---|---|---|---|---|---|---|
| Alameda | Four Stars | 91% | 88% | 30% | 55% | 77% | 8.8% |
| Alpine | One Stars | 99% | 0% | -- | -- | -- | -- |
| Amador | Two Stars | 99% | 99% | 17% | 34% | 60% | 15.5% |
| Butte | Two Stars | 99% | 99% | 24% | 42% | 67% | 12.9% |
| Calaveras | Two Stars | 99% | 99% | 13% | 27% | 48% | 20.8% |
| Colusa | One Stars | 99% | 0% | -- | -- | -- | -- |
| Contra Costa | Four Stars | 97% | 94% | 28% | 51% | 76% | 9.5% |
| Del Norte | One Stars | 99% | 0% | -- | -- | -- | -- |
| El Dorado | Three Stars | 99% | 99% | 26% | 45% | 72% | 11.2% |
| Fresno | Three Stars | 99% | 99% | 26% | 47% | 71% | 11.2% |
| Glenn | One Stars | 89% | 0% | -- | -- | -- | -- |
| Humboldt | Two Stars | 99% | 96% | 19% | 37% | 61% | 15.2% |
| Imperial | Two Stars | 99% | 99% | 15% | 30% | 53% | 18.4% |
| Inyo | One Stars | 99% | 0% | -- | -- | -- | -- |
| Kern | Two Stars | 99% | 99% | 21% | 39% | 63% | 13.7% |
| Kings | Four Stars | 86% | 82% | 31% | 55% | 76% | 8.7% |
| Lake | Two Stars | 99% | 99% | 9% | 20% | 41% | 25.8% |
| Lassen | Two Stars | 99% | 99% | 18% | 32% | 53% | 17.8% |
| Los Angeles | Four Stars | 87% | 86% | 30% | 53% | 78% | 9.3% |
| Madera | Two Stars | 99% | 99% | 12% | 23% | 49% | 20.3% |
| Marin | Two Stars | 87% | 80% | 22% | 37% | 59% | 14.1% |
| Mariposa | One Stars | 73% | 0% | -- | -- | -- | -- |
| Mendocino | Two Stars | 99% | 99% | 11% | 21% | 41% | 24.8% |
| Merced | Two Stars | 99% | 99% | 15% | 31% | 52% | 17.6% |
| Modoc | One Stars | 99% | 0% | -- | -- | -- | -- |
| Mono | One Stars | 99% | 0% | -- | -- | -- | -- |
| Monterey | Two Stars | 92% | 90% | 16% | 33% | 59% | 16.7% |
| Napa | Two Stars | 99% | 97% | 20% | 38% | 62% | 13.6% |
| Nevada | Two Stars | 99% | 99% | 20% | 39% | 68% | 13.0% |
| Orange | Four Stars | 99% | 94% | 29% | 51% | 76% | 9.6% |
| Placer | Three Stars | 99% | 99% | 28% | 49% | 74% | 10.2% |
| Plumas | One Stars | 72% | 0% | -- | -- | -- | -- |
| Riverside | Two Stars | 99% | 99% | 21% | 40% | 65% | 13.6% |
| Sacramento | Three Stars | 99% | 99% | 26% | 46% | 71% | 11.0% |
| San Benito | Four Stars | 89% | 89% | 29% | 54% | 77% | 9.0% |
| San Bernardino | Two Stars | 99% | 99% | 23% | 43% | 69% | 12.1% |
| San Diego | Four Stars | 98% | 93% | 30% | 52% | 77% | 9.5% |
| San Francisco | Three Stars | 99% | 99% | 28% | 50% | 73% | 10.1% |
| San Joaquin | Two Stars | 99% | 99% | 21% | 40% | 60% | 13.6% |
| San Luis Obispo | Three Stars | 99% | 99% | 24% | 47% | 70% | 11.3% |
| San Mateo | Four Stars | 92% | 89% | 32% | 57% | 80% | 8.2% |
| Santa Barbara | Two Stars | 92% | 92% | 18% | 36% | 61% | 15.1% |
| Santa Clara | Four Stars | 89% | 86% | 37% | 60% | 81% | 7.6% |
| Santa Cruz | Two Stars | 91% | 86% | 20% | 40% | 64% | 14.2% |
| Shasta | Two Stars | 99% | 99% | 22% | 38% | 59% | 14.9% |
| Sierra | One Stars | 99% | 0% | -- | -- | -- | -- |
| Siskiyou | Two Stars | 99% | 99% | 12% | 25% | 47% | 21.9% |
| Solano | Three Stars | 99% | 97% | 28% | 48% | 73% | 10.6% |
| Sonoma | Three Stars | 88% | 87% | 27% | 48% | 73% | 10.4% |
| Stanislaus | Two Stars | 99% | 97% | 19% | 36% | 58% | 15.6% |
| Sutter | Two Stars | 99% | 99% | 26% | 44% | 70% | 12.1% |
| Tehama | Two Stars | 99% | 99% | 17% | 32% | 52% | 18.5% |
| Trinity | One Stars | 99% | 0% | -- | -- | -- | -- |
| Tulare | Two Stars | 99% | 99% | 20% | 37% | 60% | 15.0% |
| Tuolumne | Two Stars | 99% | 99% | 16% | 33% | 60% | 15.7% |
| Ventura | Four Stars | 92% | 90% | 33% | 58% | 84% | 8.1% |
| Yolo | Three Stars | 99% | 99% | 25% | 45% | 68% | 11.7% |
| Yuba | Two Stars | 99% | 99% | 18% | 35% | 57% | 16.0% |
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.
= Best Zestimate
= Good Zestimate
= Fair Zestimate
= Tax assessor's value, or unable to compute Zestimate accuracyDepending 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.
