Is My Home Overassessed? Assessment-Ratio Check
Tells a homeowner whether their property looks over-assessed by comparing the value the county put on it against what comparable homes actually sell for - while correcting for the assessment ratio, the single biggest reason a do-it-yourself comparison goes wrong. Many states do not assess homes at 100% of market value: Georgia assesses at 40% of fair market value, Cook County (Illinois) at 10% for residential property, and South Carolina at 4% for an owner-occupied legal residence, while California's Proposition 13 system carries a factored base-year value that is effectively full value as of the last sale or new construction. The homeowner supplies their state, the assessed value shown on their notice, a market estimate (their own or a tool's), the recent comparable sales they have found, and the assessment ratio for their jurisdiction. The tool divides the assessed value by the ratio to recover the implied market value the county is asserting, sets that side by side with the comps, and returns a plain-language over-assessed, fairly-assessed, or under-assessed verdict with the gap shown as both a dollar figure and a percentage. It deliberately does NOT reproduce any proprietary appraisal model or invent adjustments - it is a generic ratio-normalization and comp-comparison explainer, and it tells the homeowner when the gap is large enough to be worth a closer look from a full evidence packet.
Example
Input: State: Georgia (Fulton County); assessed value $200,000; market estimate $480,000; recent comps: $470,000, $485,000, $462,000 (all within 0.5 mi, similar size, sold in the last 6 months); assessment ratio: 0.40 (Georgia assesses at 40% of fair market value).
Output: First, normalize the assessed value to what the county is effectively claiming your home is worth. Georgia assesses at 40% of fair market value, so your implied market value is $200,000 / 0.40 = $500,000. This step is the whole game: if you compared the $200,000 assessed figure directly against $470,000 comps you'd wrongly conclude the county had you far too low - the $200,000 is only 40% of the value being asserted. Now compare $500,000 (the county's implied market value) against your evidence. Your own estimate is $480,000, and your three comps cluster tightly at roughly $462,000-$485,000, centering around $472,000. None look like outliers. The county's implied value sits about $28,000 above your estimate and about $28,000 above the comp center. Verdict: mildly over-assessed. The gap between the county's implied $500,000 and your comp-supported ~$472,000 is about $28,000, or roughly 5.6% high. That is a real but modest gap - worth filing if your county's appeal is free and low-effort, and worth tightening with formal comp adjustments first. Caveats: I applied no size, lot, condition, or sale-date adjustments, so a comp-by-comp grid could move the supported value up or down. Confirm the 0.40 ratio and the assessed value against your own annual notice. And in Georgia some appeal methods let the assessor argue for a HIGHER value, so weigh that before filing.
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