The basic formula: assessed value × millage rate ÷ 1,000

Property tax is calculated by taking your home's assessed value (the dollar amount your county assessor assigns to your property), multiplying it by your millage rate (the tax rate set by your local government), and dividing by 1,000. The result is your annual property tax bill.

The division by 1,000 exists because millage rates are expressed in mills — one mill equals one-tenth of one cent, or $0.001. A millage rate of 25 mills means $25 per $1,000 of assessed value. This unit is standard across all U.S. counties, though the rates themselves vary widely depending on where you live.

You do not need to memorize this formula. Your county assessor's office publishes both your assessed value and your local millage rate each year, and most tax bills show the calculation already done. But understanding how it works helps you catch errors, predict changes, and understand why your bill went up or down.

Key Takeaways

  • Your assessed value comes from your county assessor; your millage rate comes from your local government (county, city, school district, or special districts combined).
  • Millage rates are published annually and vary by location — a home worth $300,000 in one county may owe twice as much tax as an identical home in another county.
  • Your property tax bill is the sum of taxes owed to multiple entities (county, schools, fire district), each with its own millage rate.
  • You can find both your assessed value and millage rate on your tax bill, your county assessor's website, or by calling the assessor's office directly.

Where to find your assessed value

Your assessed value is determined by your county assessor's office, not by what you paid for the home or what it would sell for today. Assessors use sales data, property condition, square footage, and lot size to estimate value — but the assessment is often lower than market value, and the formula varies by state.

You can find your assessed value on your property tax bill, which arrives once or twice a year depending on your county. It is also listed on your county assessor's website, usually searchable by address or parcel number. If you do not have your bill, call your county assessor's office and give them your address; they can read it to you over the phone or email it.

Some states allow homeowners to claim a homestead exemption, which lowers the assessed value used for tax calculation. If you own and live in the home as your primary residence, you may be may have access to to this reduction. The exemption amount varies by state — it might be a flat dollar amount or a percentage of value. Check your county assessor's website or call to see if you may have access to and whether you need to file a form to claim it.

Where to find your millage rate

Your millage rate is not a single number — it is the sum of rates set by multiple taxing bodies in your area. Your county sets one rate, your city or township sets another, your school district sets another, and special districts (fire, library, water, sewer) each set their own. All of these rates are added together to create your total millage rate.

Your property tax bill lists the total rate and often breaks it down by entity. You can also find millage rates on your county assessor's website, your city or county clerk's website, or your school district's website. Rates are set annually, usually in late summer or early fall, and take effect on January 1 of the following year.

If you want to know how much of your tax bill goes to schools versus county services versus fire protection, look at your bill's breakdown. It shows the millage rate for each entity and the dollar amount you owe to each one. This breakdown is useful if you are comparing two homes in different areas or trying to understand why your bill changed.

A worked example: calculating your tax bill

Suppose your home has an assessed value of $250,000 and your total millage rate is 35 mills. Here is the calculation:

$250,000 × 35 ÷ 1,000 = $8,750 per year

If your county breaks that 35 mills into components — say, 10 mills for county services, 20 mills for schools, 3 mills for fire district, and 2 mills for library — you can calculate what you owe each entity separately. County: $250,000 × 10 ÷ 1,000 = $2,500. Schools: $250,000 × 20 ÷ 1,000 = $5,000. Fire: $250,000 × 3 ÷ 1,000 = $750. Library: $250,000 × 2 ÷ 1,000 = $500. Total: $8,750.

If your assessed value changes next year to $260,000 but the millage rate stays at 35 mills, your new bill is $260,000 × 35 ÷ 1,000 = $9,100. If your assessed value stays at $250,000 but the millage rate rises to 37 mills (because the school district raised its rate), your new bill is $250,000 × 37 ÷ 1,000 = $9,250. Either change results in a higher bill.

Why your assessed value and millage rate change

Assessed values are updated periodically — some counties do it every year, others every three to five years. When your home is reassessed, the new value reflects changes in the local real estate market, improvements you made to the property, or simply a routine revaluation. If you made major renovations (new roof, addition, major renovation), your assessed value may increase. If your neighborhood's property values fell, your assessment may decrease.

Millage rates change when local governments adjust their budgets. If your school district needs more money, it may raise its millage rate. If your county has a budget surplus, it may lower its rate. These decisions are made by elected officials and are public record — you can attend budget meetings or review the decisions on your county or city website.

Some states cap how much assessed values can increase in a single year, even if the market value of homes rises sharply. These caps protect homeowners from sudden tax spikes but can also mean your assessed value lags behind market value. Check your state's rules on assessment caps and exemptions — they vary significantly.

What to do if your calculation does not match your bill

If you calculate your tax using the formula and get a different number than what appears on your bill, the most common reason is that you are using an outdated assessed value or millage rate. Tax bills are mailed months after rates are set, so the bill in your hand reflects rates from the prior year's budget cycle.

Another reason for a mismatch is that your bill may include other charges — late fees, special assessments for infrastructure projects, or county services you did not account for. Read the bill line by line to see what each charge covers.

If you believe your assessed value is wrong, you have the right to challenge it. Most counties have a formal appeal process, usually called a "property tax appeal" or "assessment appeal." You must file within a set window (often 30 to 45 days of receiving your bill) and provide evidence — recent sales of comparable homes, a professional appraisal, or documentation of property damage. Contact your county assessor's office for the appeal form and deadline.

Frequently Asked Questions

Does the millage rate include school taxes?

Yes. School district millage is part of your total rate. Your bill breaks down how much goes to schools, county services, fire, and other entities. If you want to know your school tax specifically, look at the school district's millage rate on your bill and calculate it separately using the same formula.

Can I lower my property tax by lowering my assessed value?

You cannot lower it yourself, but you can challenge your assessment if you believe it is too high. File an appeal with your county assessor within the deadline shown on your bill. You will need evidence — comparable sales, an appraisal, or proof of damage — to support your claim.

What happens if I disagree with the millage rate?

Millage rates are set by elected officials through a public budget process. You can attend budget meetings, submit written comments, or contact your county commissioners, city council, or school board members. Rates are set annually, so you have a window each year to voice concerns before the new rate takes effect.

Why do two identical homes in different counties have different tax bills?

Because millage rates vary by location. A home worth $300,000 in a county with a 25-mill rate owes $7,500 in tax. The same home in a county with a 40-mill rate owes $12,000. The difference reflects different local government budgets, service levels, and funding priorities.

Is there a way to estimate my tax bill before I buy a home?

Yes. Find the millage rate for the county and city where the home is located (usually on the county assessor's or city clerk's website), then multiply the home's purchase price by the millage rate and divide by 1,000. This gives a rough estimate, though your actual assessed value may be lower than the purchase price depending on your state's assessment rules.