What Is Assessment Ratio?

The percentage of a property's market value that a state uses to calculate the assessed value for property tax purposes.

Detailed Explanation

The assessment ratio is the bridge between what your home is worth on the open market and the number the county actually uses to calculate your tax bill. Every state sets its own ratio, and the range is enormous. In states that assess at 100% of market value (like Texas, California, and Florida), your assessed value should theoretically equal what your home would sell for. But in states with lower ratios, the assessed value is a fraction of the market price. For example, South Carolina assesses owner-occupied homes at just 4% of market value, so a $300,000 home would have an assessed value of $12,000. The millage rate is then applied to that $12,000 figure, not the full $300,000. Understanding your state's ratio is critical because it determines whether your assessment is actually too high. If your state assesses at 25% and your home is worth $400,000, your assessed value should be around $100,000. If the county has you at $120,000, you're overassessed by $20,000 in assessed value, which translates to a $80,000 overestimate of your market value.

How It Varies by State

South Carolina4%

Lowest in the nation for owner-occupied homes. Investment properties assessed at 6%.

Tennessee25%

Residential property assessed at 25% of appraised value. Commercial at 40%.

Georgia40%

All property assessed at 40% of fair market value statewide.

Ohio35%

County auditors assess at 35% of market value. Reassessment every 6 years.

Texas100%

Assessed at full market value. No state income tax, so property taxes are higher.

Alaska100%

Full market value. Many boroughs offer generous senior exemptions.

Common Misconceptions

Myth:A lower assessment ratio means lower taxes

Reality:States with low ratios often compensate with higher millage rates. South Carolina's 4% ratio comes with some of the highest mill rates in the country.

Myth:The assessment ratio is the same for all property types

Reality:Most states apply different ratios to residential, commercial, and agricultural property. In Tennessee, homes are assessed at 25% while commercial property is assessed at 40%.

Myth:If my state assesses at 100%, my assessment should match my Zillow estimate

Reality:Zillow estimates are not official appraisals. Counties use their own mass appraisal methods, which may diverge significantly from online estimates. The county's assessment date also matters.

Impact on Your Tax Bill

In Ohio (35% ratio), if your home is worth $250,000, your assessed value should be $87,500. If the county has you at $100,000 assessed ($285,714 implied market value), you're overpaying. At Ohio's average effective rate of 1.59%, that $12,500 overassessment costs you about $199 per year in excess taxes.

Property Tax Assessment Ratios by State: Complete 2026 Guide

Every state's property tax assessment ratio for 2026 — from 4% (South Carolina) to 100% (Texas, California). How to use your ratio in an appeal with worked examples.

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Learn how to appeal your property taxes step by step. Covers assessment ratios, comparable sales evidence, filing deadlines by state, and what to say at your hearing.