California Property Tools

California Property Tax Calculator

Estimate your current Proposition 13 assessed value and annual property tax using your purchase price, purchase date, and county.

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1975–2026

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Do you know the current assessed value shown on the county tax bill?

How it works

  1. A purchase commonly establishes a new base-year value equal to the purchase price.
  2. Proposition 13 generally limits annual increases using the official California inflation factor, capped at 2% (and sometimes lower).
  3. The calculator applies those official historical factors year by year from the first applicable January 1 lien date.
  4. An estimated county rate is then applied to the estimated assessed value to produce the annual and monthly tax.

What is not included

Your actual bill may also contain:

  • Mello-Roos community facilities district charges
  • Parcel taxes and special assessments
  • Voter-approved debt not fully reflected in the county-average estimate
  • Supplemental assessments after a purchase or new construction

It also does not model temporary Proposition 8 decline-in-value reductions. See the methodology for full details and data sources.

Frequently asked questions

What does this calculator estimate?
It estimates a property's Proposition 13 factored base-year value — its normal Prop 13 assessment path from the purchase price and official historical inflation factors — and the resulting annual and monthly property tax using a county-level estimated rate. It is not the county's official enrolled taxable value.
How is the assessed value calculated?
A purchase commonly establishes a new base-year value equal to the purchase price. Proposition 13 then limits annual increases to the official California CPI inflation factor, capped at 2%. We compound the purchase price by each year's official factor from the first applicable January 1 lien date through the current assessment year.
Why isn't the increase always 2%?
The annual inflation factor is based on the change in the California Consumer Price Index and is capped at 2%, but several years have been lower — for example the 2021-22 factor was about 1.036%, and 2010-11 was actually negative.
Does this include Mello-Roos and special assessments?
No. Version 1 estimates the 1% general levy plus county-typical voter-approved debt applied to assessed value. It does not include parcel-specific direct charges such as Mello-Roos, parcel taxes, or special assessments, which can meaningfully increase an actual bill.
Why might my county tax bill differ from this estimate?
The county's official taxable value can be lower due to a temporary Proposition 8 decline-in-value reduction, or different because of new construction, later ownership changes, base-year-value transfers, exemptions, escape assessments, disaster relief, or assessor corrections.

Inflation factors cover assessment years through 2026-27. Data last reviewed January 2026.