Assessment check

Is your property tax assessment high for your area?

Enter what you paid, when, your ZIP, and the assessed value and valuation date from your notice. You get what your home was worth on that date if it grew like your area did, and your assessment as a share of it, from the federal FHFA index with the math shown.

Your assessment against the index

Fill in the fields and press the button. The example below is a real index result with a made-up $520,000 assessment.

Informational only, not legal, tax or professional advice and not an appraisal. The index figure is an area average; appeal rules and assessment ratios are set locally.

Methodology

The implied value. What you paid × (index at the valuation date ÷ index at purchase), on the FHFA House Price Index for the smallest of your ZIP, county, metro or state with data for both dates, the same series and area the value estimate uses. State and metro indexes are quarterly, so a date is matched to its quarter; county and ZIP indexes are annual, so it is matched to its year (annual files dated March 31, 2026; quarterly master file through 2026 Q2).

The share. Assessed value ÷ implied value. Many states and counties assess at a fixed fraction of market value, and the notice or the assessor’s site states that ratio; the share here is the number to set beside it. The tool also shows the same assessment against today’s estimate, which is a different question: how far the market has moved since the valuation date.

What it stops short of. It does not say an assessment is wrong. Assessors use sales, records and sometimes inspections of the house itself; the index knows only the area. It does not model exemptions, caps on annual assessment increases, or the tax rate, so it says nothing about the bill.

What this comparison cannot know

Your house. The implied value tracks the area’s average. Renovations, condition and lot are not in it, and an assessor may have counted them.
Sales the index never sees. Per FHFA’s own description, the index is built from repeat sales and appraisals on conforming mortgages. Cash, jumbo, FHA and VA purchases are not in it.
Local rules. Assessment ratios, valuation dates, caps, exemptions and appeal deadlines differ by state and county and change over time. Read them off your notice.
The future. The index is history. It is not an appraisal and not a forecast.

Last reviewed: September 2026. Data vintage: FHFA master file 2026 Q2; annual county and ZIP files dated March 31, 2026.

Frequently asked questions

What is the difference between assessed value and market value?

Market value is what a home would sell for. Assessed value is the figure your local assessor puts on it for the property tax bill, often a fixed share of market value set by state or local law, and often based on a valuation date months or years before the bill. This tool gives you an index-based stand-in for market value on that valuation date, so the two can be compared on the same day.

My assessment is below the index figure. Is that wrong?

Usually not. Many jurisdictions assess at a stated fraction of market value, and assessments tend to lag the market because they are updated on a schedule. Compare the share this tool shows with the assessment ratio your notice or assessor's site states. A share close to that ratio is what a normal assessment looks like.

Can I use this to appeal my assessment?

It can tell you whether your assessment sits above or below an area-average benchmark for the same date, which is a reason to look closer. An appeal is decided on local rules and evidence: comparable sales near the valuation date, errors in the property record, and condition. An index figure is not a comparable sale and assessors are not bound by it.

Which date should I enter?

The valuation date printed on the notice (often January 1 of the tax year), not the date the notice arrived or the date the bill is due. The index is matched to the quarter or year holding that date, so a January 2025 valuation is read against the state's 2025 Q1 index or the ZIP's 2025 annual index.

Guides

Is My Property Tax Assessment Too High? Check It Against the IndexAssessed value is not market value. How to work out what the FHFA index implies your home was worth on the valuation date, and read your assessment as a share of it.

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