This is an estimate for planning, from Zillow's ZIP-wide typical values applied to your purchase price. It is not an appraisal, a broker price opinion, an offer, a loan offer, or tax or legal advice, and Rudy is a real estate agent, not a lender, appraiser or tax professional.
How the estimate works
- Step one compares the Zillow index for your property type and ZIP code at your purchase date with the newest month published.
- The percentage change between them is applied to your price, and the condition choice frames the range.
- A loan you still carry is amortized on a regular fixed-rate schedule, with payments counted from the month after purchase.
- Equity is the mid-range value less what you owe; the net figure also deducts selling costs and ignores taxes.
- The Prop 13 value multiplies your price by every annual factor the State Board of Equalization has published, at most 2% each.
Your Prop 13 value and Prop 19
One of the less visible effects of rising values is the spread between market value and taxable value. Under Prop 13, taxable value starts at the sale price and increases by 2% a year or less, so the spread widens in strong markets.
Proposition 19 lets eligible owners, including those 55 or older, transfer a taxable value to the next home they buy in California, provided the purchase comes within two years of the sale; the limit is three transfers. The county assessor rules on each claim.
To read further, open the downsizing calculator and Prop 13 by the numbers: assessed versus market value.
Sources and dates
- Zillow Research, Zillow Home Value Index (ZHVI) by ZIP code: all homes, single-family and condo; middle tier, smoothed and seasonally adjusted (data through September 2026, files updated Oct 16, 2026)
- FHFA House Price Index for five-digit ZIP codes (annual, developmental index, not seasonally adjusted; 2000 = 100), used only for purchases before Zillow's series begin. Citation: Bogin, Doerner and Larson, Local House Price Dynamics: New Indices and Stylized Facts, FHFA Working Paper 16-01 (annual, through 2025)
- Freddie Mac Primary Mortgage Market Survey (PMMS): weekly 30-year and 15-year fixed averages; the page uses the mean for your purchase month (monthly means through October 2026; latest weekly 30-year average 7.24% on Oct 29, 2026)
- California State Board of Equalization, Letter To Assessors No. 2026/002: inflation factors for 1976-77 through 2026-27, with Revenue and Taxation Code section 51 and California Constitution article XIII A, section 2(b) (January 13, 2026)
- California State Board of Equalization, Proposition 19 (checked Oct 30, 2026)
- Assumptions, not sourced figures: the condition range (the same rule of thumb as the home value range tool), 6% selling costs, 20% down, regular payments on a fixed-rate loan starting the month after you bought, and the first inflation factor applying on the first January 1 after your purchase
Questions owners ask
How should I read the range?
The middle is your price moved by the ZIP-wide index; the range is a rule of thumb for condition, not a statistical margin. Your home's view, lot and updates can put it outside the range, and a free comparable-sales review from Rudy shows where it falls.
Why use ZIP data instead of nearby sales?
Sales happen irregularly, while Zillow's ZIP index is published every month back to 2000. That makes it a clean way to measure change since you bought; the sales come in when you want a value for your exact home.
My loan is not the one I bought with. What now?
If you refinanced or added a home equity line, switch to the balance option and type the total you owe now; no payment estimate is needed then.
Why is my taxable value so much lower?
Prop 13 caps the yearly increase at 2%, while market values have often risen faster. The taxable value on your bill is not an estimate of what the home would sell for.
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