1. Your home and your notice
Tax rate: mills divided by 10 (18.5 mills is 1.85%). The assessment ratio and rate are printed on the notice or at the assessor's site. Leave the rate blank to see values without dollars.
2. Comparable sales
One sale per line: label, sale price, sq ft, beds, baths, lot sq ft, year built, months since sale, assessed value. Only the price is required; blank fields are not adjusted. Leave commas out of numbers (or separate fields with tabs or semicolons). Lines starting with # are ignored. The assessed value column powers the equity test and needs at least three homes.
Adjustment rates and appeal costs (defaults are rules of thumb, change them)
3. What the numbers say
Market value
| Measure | Indicated value | Over-assessed by | Assessment cut | Tax saved / yr |
|---|
Equity (assessment per sq ft)
Does filing pay?
Adjusted comparables
| Comparable | Sale price | Adjustments | Adjusted | Gross % | Note |
|---|
How it works, and what it leaves out
Model. Adjusted comp = sale price + time drift + (your sq ft − comp sq ft) × $/sq ft + bedroom, bath, lot and age differences × your rates. Comps that needed more than 25% gross or 15% net adjustment are flagged weak. The indicated value weights each comp by how little it needed adjusting; the conservative figure is the lower quartile of adjusted values. The equity value is the median assessed $/sq ft of your comps times your square footage.
Not modelled. Condition, view, finished basement, garage, upgrades, deed restrictions, homestead caps and exemptions, assessment-limit rules, the board's own deadlines and evidence formats, and the chance a board agrees with you. The rates above are rules of thumb, not local market data: a defensible appeal uses paired sales or an appraiser's rates.
Reconciles. The tax saved is the assessment reduction times the rate you entered, nothing else. A jurisdiction that recalculates other levies or drops an exemption after a cut can change the real figure.
The numbers are estimates that depend entirely on the figures you provide. Check the filing deadline on your notice; it is often 30 to 90 days.
How do I know if my property is over-assessed?
Compare the market value your assessment implies with what similar nearby homes actually sold for, after adjusting each sale for size, bedrooms, bathrooms, lot, age and how long ago it sold. This tool does that arithmetic from figures you type in, and also compares your assessment per square foot with the assessments of the same homes.
How many comparable sales do I need for a property tax appeal?
Three to six recent, nearby, similar sales is the usual ask. With fewer than three, or with sales older than about twelve months, boards tend to discount the case. The tool flags both.
What is the assessment ratio?
In many jurisdictions the assessed value is a set percentage of market value (for example 100 percent, or 33.3 percent). The tool converts your assessment to the market value it implies using the ratio you enter, so a 100 percent and a 40 percent jurisdiction are both handled. Your notice or assessor's office states the ratio.
What does it cost to appeal, and when is it worth it?
Many boards charge a small filing fee or none, and the yearly tax saved is the assessment reduction times your tax rate. The tool shows the saving, the net over the years you expect it to hold, the win probability at which the appeal breaks even, and what a contingency appeal firm would keep out of the same saving.
Is my data uploaded anywhere?
No. Everything runs in this browser tab. There are no accounts, cookies or analytics vendors, and no property data leaves your device.