Prop 13 Assessment Growth Simulator
See how your assessed value compounds at the constitutional 2% cap over time — and why it can lag far behind market value.
Under Prop 13, your home's taxable assessed value can grow by at most 2% per year (or the CPI change, if lower), regardless of how much market values rise — as long as you don't sell or add new construction. Over 20-30 years of ownership, this compounding cap can leave your assessed value far below current 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 — the same math a county assessor applies absent a sale or new construction.
In reality, the actual annual increase is the lesser of 2.0% or the California CPI change for that year, so some years see smaller increases than this simulator's steady-2%-every-year projection; treat this as a ceiling estimate, not a guarantee. Remember that any change of ownership or completed new construction resets some or all of the assessed value to current market value at that point, breaking the compounding chain shown here.
The estimated tax figure applies your entered effective rate (or a 1.1% default, reflecting the 1% base rate plus typical voter-approved local bonds) to the projected assessed value — it does not include any exemptions like the Homeowners' Exemption, which would reduce the taxable amount further.
Frequently Asked Questions
How much can my property's assessed value increase each year under Prop 13?
By law, no more than 2% per year, or the actual change in the California Consumer Price Index if lower — whichever is less. This is a cap on the assessed value, not on your final tax bill, which can still rise faster due to 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 underlying assessed value growth. Apply any exemptions (like the $7,000 Homeowners' Exemption) or additional voter-approved assessments separately when estimating your actual 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. Actual annual increases depend on CPI and are subject to change of ownership or new construction reassessments this simulator cannot predict.