The basic formula: assessed value times mill rate divided by 1,000

Property tax is calculated by taking your home's assessed value, multiplying it by the mill rate, then dividing by 1,000. The mill rate is a tax rate expressed per $1,000 of assessed property value. Your county or municipality sets both the assessed value and the mill rate each year.

Here is the actual calculation: (Assessed Value × Mill Rate) ÷ 1,000 = Annual Property Tax. If your home is assessed at $300,000 and your mill rate is 15 mills, your calculation would be ($300,000 × 15) ÷ 1,000 = $4,500 in annual property tax.

The term "mill" comes from an old word meaning one-thousandth. A mill rate of 15 means $15 in tax per $1,000 of assessed value. Mill rates vary widely by location — a county might have a rate of 8 mills, while a neighboring county has 22 mills. Your property tax bill reflects the combined mill rates of every taxing body that covers your address: the county, the school district, the city or township, and sometimes special districts for fire, water, or library services.

Key Takeaways

  • The mill rate is the tax rate per $1,000 of assessed value, and you multiply your assessed value by the mill rate, then divide by 1,000 to get your annual tax bill.
  • Your assessed value is not the same as your home's market value — it is set by your county assessor and may be lower or higher depending on local assessment practices.
  • Your total mill rate is the sum of rates from every taxing body that covers your property: county, school district, city, and any special districts.
  • Mill rates change each year and are published by your county assessor or tax collector before bills are mailed, usually in spring or early summer.

Where to find your assessed value and mill rate

Your assessed value appears on your property tax bill, usually near the top. If you do not have a recent bill, you can find it on your county assessor's website — most counties now publish searchable databases where you enter your address or parcel number and see the assessed value, the breakdown of mill rates by taxing body, and sometimes a calculation showing how your bill was computed.

The mill rate for your specific property is also on your tax bill, though it may be listed as a single combined rate or broken down by taxing body. If your bill shows only a total amount due, call your county tax collector's office and ask for the mill rate or the rate breakdown. They can tell you the rate for the county, school district, city, and any special districts that tax your parcel.

Some counties publish mill rates in a public notice in the spring or early summer before tax bills are mailed. Check your county assessor's website or the county clerk's office for the current year's rates. Mill rates change annually based on the county's budget needs and the total assessed value of all property in the taxing district.

Why assessed value is different from what your home is worth

Your home's assessed value is not the same as its market value — the price it would sell for today. The assessor estimates assessed value using sales data, property condition, and local market trends, but the goal is to create a fair basis for taxation across all properties in the county, not to match each home's exact market price.

Some counties assess property at 100 percent of market value. Others assess at a lower percentage — 50 percent, 60 percent, or some other fraction set by state law. A few states use different assessment rates for different property types: residential property might be assessed at 50 percent of value while commercial property is assessed at 100 percent. Your state's Department of Revenue or your county assessor's office can tell you the assessment rate used in your area.

The assessed value is also not updated every year in every county. Some counties reassess all property annually. Others reassess on a cycle — every three years, every five years, or only when the property changes hands. If your home has not been reassessed in several years, its assessed value may be significantly lower than its current market value, which means your tax bill is lower than it would be if the assessment were current.

How to verify the calculation on your tax bill

Once you have the assessed value and the mill rate, you can check the math yourself. Write down the assessed value from your bill. Find the mill rate — it may be listed as a single number or as separate rates for county, school, city, and special districts. Add up all the separate rates if they are listed separately.

Multiply the assessed value by the mill rate. Then divide by 1,000. The result should match the tax amount shown on your bill, or be very close — within a dollar or two, because some bills round differently or include small adjustments you may not see listed.

If your calculation does not match the bill, check whether the bill includes other charges: late fees, special assessments, or payments toward a bond issue. These are added to the property tax but are not part of the mill rate calculation. If you subtract those and the numbers still do not match, contact your county tax collector's office and ask them to walk you through the calculation.

What happens when mill rates change year to year

Mill rates are set by each taxing body — the county commission, the school board, the city council — based on their budget for the coming year. If a school district needs more money, it may raise its mill rate. If a county has a budget surplus, it may lower its rate. The total mill rate you pay is the sum of all these individual decisions.

Your county assessor publishes the new mill rates before tax bills are mailed, usually in spring or early summer. You can find them on the assessor's website or by calling the office. If you see a big jump in your tax bill, it could be because the mill rate increased, because your assessed value increased, or both.

Some states allow homeowners to challenge their assessed value if they believe it is too high. The process and important date vary by state — some allow challenges every year, others only in certain years or only if the assessment changed. Your county assessor's office can tell you whether you have the right to challenge and what the important date is.

Mill rate examples in different scenarios

Suppose you live in a county where the county mill rate is 8, the school district rate is 12, the city rate is 5, and a fire district rate is 2. Your total mill rate is 27 mills. If your home is assessed at $250,000, your calculation is ($250,000 × 27) ÷ 1,000 = $6,750 in annual property tax.

Now suppose you move to a neighboring county where the same home would be assessed at $280,000 (because that county's assessments are higher) and the combined mill rate is 18. Your calculation there would be ($280,000 × 18) ÷ 1,000 = $5,040. Even though the home is worth more in the second county, your tax bill is lower because the mill rate is much lower.

If your county reassesses your home and the assessed value rises from $250,000 to $275,000, but the mill rate stays at 27, your new bill is ($275,000 × 27) ÷ 1,000 = $7,425 — an increase of $675. If the mill rate also rises from 27 to 30 mills in the same year, your bill would be ($275,000 × 30) ÷ 1,000 = $8,250, an increase of $1,500 from the original bill.

Frequently Asked Questions

Is the mill rate the same for every property in my county?

The mill rate is the same for all properties in the same taxing district, but taxing districts do not always match county lines. Your property is covered by multiple taxing bodies — county, school district, city, and possibly special districts — and each has its own mill rate. Two homes in the same county but in different school districts or cities will have different total mill rates.

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

You cannot lower your assessed value yourself, but you may be able to challenge it if you believe it is too high. The process and important date vary by state. Some states allow annual challenges, others only in certain years. Contact your county assessor's office to learn whether you have the right to challenge and what evidence you need — usually a recent appraisal or sales data for comparable homes.

What if my mill rate is listed as a decimal instead of a whole number?

Some counties express mill rates as decimals — for example, 0.015 instead of 15 mills. The calculation is the same: multiply your assessed value by the rate, then divide by 1,000. If the rate is already expressed as a decimal per dollar (0.015), you can skip the division step and multiply directly. Check your tax bill or call your assessor to confirm which format your county uses.

Why did my property tax bill go up if the mill rate stayed the same?

If the mill rate did not change but your bill increased, your assessed value went up. This usually happens during a reassessment year. Check your current bill against last year's bill and compare the assessed values. If the assessed value increased, that is why your bill is higher. If you believe the new assessment is too high, ask your assessor about the challenge process.