If you have ever looked at your property tax bill and seen a number like "45 mills," you might have wondered what that actually means. Mill rates are the language of property taxation in many parts of the United States — and understanding them is essential to knowing what you pay and why.
A mill is one-tenth of one cent, or $1 of tax for every $1,000 of assessed property value. A millage rate of 45 mills means you pay $45 in tax for every $1,000 of assessed value. On a home with an assessed value of $200,000, that works out to $9,000 per year in property taxes.
How Mill Rates Work
Mill rates are set by each taxing authority that has jurisdiction over your property. In most areas, this includes the county government, city or municipality, school district, and any special districts (fire, water, library, etc.). Each entity sets its own mill rate, and the total mill rate on your property is the sum of all these individual rates.
For example, if your county charges 15 mills, your city charges 12 mills, your school district charges 18 mills, and a special fire district charges 3 mills, your total millage rate is 48 mills.
Mill Rate vs. Effective Tax Rate
Mill rates and effective tax rates measure the same thing — how much tax you pay relative to your property's value — but they express it differently.
The mill rate is applied to assessed value, which may or may not equal market value. Some states assess at 100% of market value, while others assess at 50%, 40%, or even 10%. The effective tax rate shows what you actually pay as a percentage of your home's market value, making it easier to compare across jurisdictions.
For example, a county with a 50-mill rate and 100% assessment ratio has the same effective rate (5.0%) as a county with a 100-mill rate and a 50% assessment ratio.
States That Use Millage Rates
Millage rates are most commonly used in the Southeast and parts of the Midwest. Alabama, Georgia, and Florida are among the states where millage is the standard terminology. In these states, property tax bills typically break down each taxing authority's mill rate separately.
Even in states that do not use the term "mill," the underlying math is the same. A tax rate of 1.5% is equivalent to 15 mills. The terminology varies, but the concept is universal.
Why Mill Rates Change
Millage rates are adjusted annually (or bi-annually) by each taxing authority based on budget needs. When a school district needs to build a new facility, it may raise its mill rate. When property values rise significantly, taxing authorities may lower their mill rates to collect the same total revenue — though this does not always happen.
Understanding mill rates helps you anticipate tax changes. If your county announces a 5-mill increase, you can calculate exactly what that means for your bill: $5 more per $1,000 of assessed value.
Data source: U.S. Census Bureau, American Community Survey (ACS) 5-Year Estimates (2019-2023). All figures are estimates and may differ from actual tax bills due to exemptions, abatements, and local assessment practices.