Prop 13 Assessment Growth Simulator
See how your assessed value grows under Prop 13's 2% annual cap, and why it can fall far behind market value.
Under Prop 13, your home's taxable assessed value can rise by at most 2% a year (or the CPI change, if lower), however much market values rise, as long as you don't sell or add new construction. Over 20 to 30 years of ownership, that cap can leave your assessed value far below market value.
Enter your current assessed value and a number of years to project forward.
Prop 13 Assessment Growth Simulator
Projected Assessed Value
Total Growth
Est. Annual Tax Then
| Year | Assessed Value |
|---|
How this is calculated
Each year, the tool multiplies the prior year's assessed value by 1 + 2.0% (the constitutional maximum), compounding annually. A county assessor applies the same math when there is no sale or new construction.
The annual increase is the lesser of 2.0% or that year's California CPI change, so in some years the increase is smaller than the steady 2% this simulator assumes. Treat the result as a ceiling. A change of ownership or completed new construction resets some or all of the assessed value to market value at that point, and the projection no longer applies.
The estimated tax applies the effective rate you enter (or a 1.1% default, which is the 1% base rate plus typical voter-approved local bonds) to the projected assessed value. It does not include exemptions such as the Homeowners' Exemption, which would lower the taxable amount.
Frequently Asked Questions
How much can my property's assessed value increase each year under Prop 13?
By law, no more than 2% a year, or the change in the California Consumer Price Index if that is lower. The cap applies to assessed value, not to your tax bill, which can rise faster because of voter-approved local bonds and assessments.
Does the 2% cap apply forever, or can my assessment jump suddenly?
The cap applies as long as ownership doesn't change and there's no new construction. A change of ownership or completed new construction (like an addition) triggers a reassessment to full current market value for that portion, resetting the base year value from that point forward.
Why is my neighbor's tax bill so different from mine for a similar house?
Because Prop 13 assesses based on purchase price plus capped annual growth, not current market value. A longtime owner's assessed value can be far below a recent buyer's purchase price for an identical home next door.
Does this simulator include exemptions like the Homeowners' Exemption?
No. This tool projects only the growth in assessed value. Apply any exemptions (such as the $7,000 Homeowners' Exemption) and any voter-approved assessments separately when you estimate your tax bill.
What tax rate should I use to estimate my dollar amount?
The base rate is 1% of assessed value under Prop 13, but most California parcels also carry voter-approved local bonds and assessments, pushing the typical effective rate to roughly 1.1%-1.2%. Check your county assessor's site for your parcel's exact combined rate.
This tool provides an educational estimate only and is not tax advice. Annual increases depend on CPI, and a change of ownership or new construction triggers a reassessment this simulator cannot predict.