California Proposition 13 Property Tax Calculator

How this calculator works

California property tax is governed by a 48-year-old constitutional amendment that still controls every parcel in the state: Proposition 13, passed by California voters on June 6, 1978 with roughly 65% support and added as Article XIIIA of the California Constitution. Forty-eight years later, every California property-tax bill still flows from the same four mechanics: a 1% cap on the ad-valorem base rate, a 2% annual cap on assessed-value growth, reassessment to market value at every change of ownership, and reassessment of the changed portion on substantial new construction. Cal. Rev. & Tax Code §§ 50–100 implement these rules.

This calculator computes a property's annual ad-valorem tax under the current framework, including the Proposition 19 (2020) modifications to the parent-child / grandparent-grandchild exclusion (Cal. Rev. & Tax Code § 63.2) and the 55+/severely disabled portability allowance (§ 69.6). The most important effect of Prop 13 — and the source of California's most distinctive property-tax outcomes — is the compound growth gap between assessed and market value over a long hold. This calculator surfaces that gap explicitly.

The four mechanics of Prop 13

1. 1% base ad-valorem rate cap (Cal. Const. Art. XIIIA § 1(a)). The county-and-state base property tax rate cannot exceed 1% of assessed value. Voter-approved general-obligation bond debt is added on top under § 1(b); typical California combined rates run 1.10%–1.30% depending on the jurisdiction's bond activity. Mello-Roos special taxes under Cal. Gov. Code § 53311 et seq. (parcel-fixed amounts, not rates) can layer further on post-1982 California subdivisions — typically $1,000–$5,000+ per year per parcel.

2. 2% annual cap on assessed-value growth (§ 2(b); Cal. Rev. & Tax Code § 51(a)(2)). Year-over-year increases in assessed value are capped at the lesser of 2% or the California CPI change. The 2% figure has historically been the binding number. The cap compounds from the base year value — the most recent change-of-ownership or new-construction reassessment event.

3. Reassessment on change of ownership (§ 2(a); Cal. Rev. & Tax Code §§ 60–69.5). Assessed value resets to full market (fair market) value at the moment of transfer. The "change of ownership" definition in § 60 is broad: any transfer of a present interest in real property whose value is substantially equal to the value of the fee. Direct sales, deed transfers, certain trust transfers, and (under § 64(c)) cumulative legal-entity changes crossing the 50% threshold all qualify.

4. Reassessment on new construction (§ 2(a); Cal. Rev. & Tax Code §§ 70–74.3). Substantial new improvements trigger reassessment of the changed portion only. An ADU addition reassesses the ADU at market; the original house keeps its base year value. Ordinary repairs and maintenance do not trigger.

A worked example — long-held home in a high-appreciation market

A Berkeley home bought in 1990 for $400,000. The current tax year is 2026. The property has not changed hands since purchase. Current estimated market value: $2,000,000. Local voter-approved bonds: 0.2% (typical Bay Area).

• Years held: 2026 − 1990 = 36 years.
• 2%-compound assessed value: $400,000 × 1.02^36 = $815,955.
• Effective assessed value: min($815,955, $2,000,000) = $815,955 (compound governs because market exceeds it).
• Prop 13 base tax: $815,955 × 0.01 = $8,160.
• Bonds tax: $815,955 × 0.002 = $1,632.
• Total annual tax: $9,791.

What would the tax be without Prop 13 — i.e., if the parcel were reassessed to current market value? $2,000,000 × 0.012 = $24,000. The annual Prop 13 savings is $14,209. Over a 10-year forward hold (assuming this differential persists at this year's level), the static savings estimate is roughly $142,000 — and that understates the real-world figure because the gap continues to widen each year as market value grows faster than 2%.

This is the structural reason California's effective property-tax rate ranks near the bottom of U.S. states despite some of the nation's highest absolute property values. The state's revenue load shifted off ad-valorem property tax onto income tax, sales tax, and parcel taxes in the years after 1978.

A worked example — recent purchase

A Palo Alto home bought in 2023 for $1,500,000. The current tax year is 2026. Estimated market value: $1,700,000. Local bonds: 0.2%.

• Years held: 3.
• 2%-compound assessed value: $1,500,000 × 1.02^3 = $1,591,812.
• Effective assessed value: $1,591,812 (under market).
• Total annual tax: $1,591,812 × 0.012 = $19,102.

Tax-if-reassessed-now: $1,700,000 × 0.012 = $20,400. Annual savings: only $1,298. Over a short hold, Prop 13's benefit is modest. The compound advantage only emerges over years.

A worked example — Prop 19 senior portability

A 70-year-old owner sells a Long Beach home she bought in 1985 for $300,000 (her base year value, now grown at 2% compound to roughly $675,660 for tax year 2026 — but she's been paying tax on a small fraction of the home's $2,000,000 market value for decades). She sells the Long Beach home and buys a $1,800,000 Sacramento home.

Under Cal. Rev. & Tax Code § 69.6 (Prop 19), because she is 55+ and the replacement primary residence is less expensive than the original ($1.8M < $2.0M), she can transfer her base year value in full. Her Sacramento home is assessed at the prior base ($675,660 compound figure), not at $1.8M. The Sacramento home's annual tax becomes roughly $8,108 instead of the $21,600 a new buyer would pay. She has used one of her three lifetime portability transfers; two remain available for future moves anywhere in California.

Prior to Prop 19 (effective April 1, 2021), this portability was governed by Props 60 (1986), 90 (1988), and 110 (1990) — a single-use, same-county-only or reciprocating-county-only rule. Only 10 of California's 58 counties had opted in to Prop 90 reciprocity, sharply limiting senior mobility within the state. Prop 19 changed all of this.

A worked example — inherited rental property under Prop 19

A parent dies leaving a rental property assessed at $200,000 (base year value from 1980). Current market value: $1,500,000. The child inherits.

Before Prop 19 (i.e., transfers occurring before February 16, 2021), the former Props 58 (1986) / 193 (1996) exclusion applied: up to $1M of assessed value per parent transferred to any property type — including rental, vacation, and commercial property — without reassessment. The child would have inherited the rental at the parent's $200,000 base year value and paid tax of roughly $2,400/year on a $1.5M property.

Under Prop 19 / Cal. Rev. & Tax Code § 63.2 (effective February 16, 2021), this exclusion no longer applies to anything except a primary residence the recipient also makes their own primary residence. The child is reassessed to market value: the rental's new base year value is $1,500,000, and the annual tax jumps to roughly $18,000. This single change — ending the broad parent-child exclusion for investment property — was the most consequential update to California property-tax law since Prop 13 itself.

Prop 19 vs the old Props 58 / 193 / 60 / 90 / 110

| Issue | Pre-Prop 19 | Post-Prop 19 (effective 2021) | |---|---|---| | Parent-child transfer of primary residence | Up to $1M of assessed value sheltered per parent | Excluded only if child makes it their primary residence within 1 year AND market-vs-taxable difference ≤ $1M | | Parent-child transfer of investment property | Up to $1M of assessed value sheltered per parent | Reassessed to market value — no exclusion | | 55+/disabled portability — number of transfers | One-time only | Up to 3 in a lifetime | | 55+/disabled portability — geography | Same county OR reciprocating county only (10 counties opted in) | Anywhere in California, no reciprocity required | | 55+/disabled portability — value cap | Replacement had to be equal or lesser value | Equal/lesser fully transfers; greater value uses prior base + difference | | Effective date | Various — Prop 58 (1986), Prop 193 (1996), Props 60/90/110 (1986–1990) | Feb 16, 2021 (parent-child); April 1, 2021 (portability) |

Cal. Rev. & Tax Code § 63.2 (parent-child) and § 69.6 (portability) are the controlling statutes. California State Board of Equalization Letter to Assessors 2020/061 is the controlling administrative guidance — every California county assessor follows it.

Why refinancing does NOT trigger reassessment

A refinance is not a transfer of ownership under Cal. Rev. & Tax Code § 60. The mortgage is a security interest, not a transfer of the fee. The owner retains the present beneficial interest; the lender holds only a contingent security interest. California homeowners can refinance freely — multiple times if rates move favorably — without losing the Prop 13 base year value.

This is one of the most-misunderstood mechanics of Prop 13 and a common source of unnecessary planning anxiety. Refinancing does not cost the homeowner anything in property-tax terms. Cashing out equity does not change the assessed value. Adding a borrower to title (e.g., a new spouse) is governed by separate rules: the spousal-transfer exclusion under § 63 covers most such additions without reassessment; transfers to non-spouse co-borrowers can trigger partial reassessment of the transferred interest only.

The "lock-in effect"

The Prop 13 compound differential creates a powerful disincentive to move. A senior who has been in a 1985 Sunset District home for 41 years is paying tax on roughly $675K of compound assessed value while a comparable just-sold house next door pays tax on $2M+. Moving to a smaller condo would increase their annual property-tax bill substantially — even if the condo is half the price of the house. Prop 19's portability allowance (up to 3 transfers anywhere in California for 55+/disabled owners) was crafted specifically to ease this lock-in for seniors, while the parent-child investment-property exclusion was tightened to end the cross-generational tax shelter.

For non-senior owners, the lock-in remains. Moving across town — even to a less expensive home — typically means a substantial property-tax increase, which combined with California capital-gains tax on the sale produces a meaningful friction cost. This is one structural factor in California's lower-than-national-average residential mobility rate.

Mello-Roos and parcel taxes

The 1% Prop 13 base rate plus voter-approved bonds (typically 0.1%–0.4%) is the ad-valorem portion of a California property tax bill. Two non-ad-valorem layers are common:

• Mello-Roos special taxes (Cal. Gov. Code § 53311 et seq.) — parcel-fixed amounts (not rates) authorized by community facilities districts (CFDs) typically formed when post-1982 California subdivisions were built. Mello-Roos bills run $1,000–$5,000+ per year per parcel and persist for the life of the CFD bond (often 30–40 years). They appear as a separate line on the tax bill labeled "CFD" or "Mello-Roos."

• Parcel taxes — flat per-parcel amounts authorized by local jurisdictions (school districts, library districts) under various two-thirds-vote provisions. Typically $50–$500 per parcel; appear as separate line items.

Neither is captured by this calculator. Pull the parcel-specific amounts directly from the latest tax bill and add them to the ad-valorem figure to get the total annual bill.

Common errors

Four mistakes turn up routinely in California property-tax math:

1. Assuming refinancing triggers reassessment. It does not. The mortgage is not a transfer of the fee.

2. Applying former Props 58/193 to a post-Feb-16-2021 parent-child transfer of investment property. The broad pre-2021 exclusion is gone. Investment property, vacation homes, and commercial property inherited from a parent on or after February 16, 2021 are reassessed to market value with no exclusion. This change is the most-missed update to California property-tax law.

3. Miscalculating the 2% compound. The cap compounds from the base year value, not the prior year's market value. A property bought for $400K in 1990 has a 2026 assessed value of $400K × 1.02^36 ≈ $815,955 — not $400K × (1 + 0.02 × 36) = $688K (linear), and not $400K × the appreciation index (market growth).

4. Forgetting voter-approved bonds on top of the 1%. The 1% Prop 13 base rate is the floor; almost every California parcel pays 1.10%–1.30% combined once general-obligation bonds are added under § 1(b). Mello-Roos parcel-fixed amounts further increase the total bill on subdivisions formed under a CFD.

What this calculator does not do

This is a planning and screening tool. It does NOT:

• Compute Mello-Roos or parcel-fixed amounts. Those are per-parcel-specific and must be pulled from the latest tax bill.

• Determine change-of-ownership status for complex entity structures. Cal. Rev. & Tax Code § 64 has detailed rules for legal-entity ownership changes (particularly the cumulative 50%-of-control test). These are case-specific and require the entity's ownership history.

• Compute the partial-reassessment math for new construction. Cal. Rev. & Tax Code §§ 70–74.3 reassess only the changed portion of the property. The math requires the value of the new construction at completion, which is determined by the county assessor.

• Apply the disaster reconstruction exclusion. § 70(c) excludes like-kind reconstruction after a Governor-declared disaster from reassessment; the exclusion is fact-specific and requires the assessor's verification.

• Estimate state or federal income tax on a sale. California capital-gains tax (treated as ordinary income up to 13.3%) and federal capital-gains tax (up to 20% plus the 3.8% NIIT) are separate calculations not modeled here.

How this page is maintained

The Prop 13 framework is constitutional (Cal. Const. Art. XIIIA) and has been unchanged in its core mechanics since 1978. The most recent material event is Proposition 19 (2020), effective February 16, 2021 (parent-child) and April 1, 2021 (portability). Various split-roll efforts (most recently Proposition 15 of 2020, which failed 52%–48%) have not modified the framework. We monitor each California election cycle and each session of the Board of Equalization for changes and refresh this calculator within 30 days of any enacted amendment or new Letter to Assessors.

Last reviewed: 2026-05-15 against Cal. Const. Art. XIIIA §§ 1, 2, 2.1, Cal. Rev. & Tax Code §§ 50–100, 63, 63.2, 69.6, and California State Board of Equalization Letter to Assessors 2020/061.