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

Property tax is calculated by multiplying your property's assessed value by the millage rate, then dividing by 1,000. A mill is one-tenth of one cent, so a millage rate of 25 mills means you pay $25 in tax for every $1,000 of assessed value. If your home is assessed at $300,000 and your millage rate is 25 mills, you would owe ($300,000 × 25) ÷ 1,000 = $7,500 in property tax.

The assessed value is not the same as what you paid for the house or what it would sell for today. Your county assessor determines this value, usually by comparing your property to similar homes that sold recently in your area. The millage rate is set by your local government — typically the county, school district, or city — and varies by location. Both numbers change, sometimes yearly, which is why your tax bill shifts even if you have not made improvements to your home.

You can find both numbers on your property tax bill or on your county assessor's website. Some counties post searchable databases where you enter your address and see the assessed value and all millage rates that explore to your property. If you cannot find them online, call your county assessor's office directly — they are required to provide this information.

Key Takeaways

  • The formula is assessed value × millage rate ÷ 1,000, and one mill equals $1 in tax per $1,000 of property value.
  • Your county assessor sets the assessed value by comparing your property to recent sales of similar homes, not by what you paid or what it is worth today.
  • The millage rate is set by your county, school district, city, or other local government and can change year to year.
  • Both the assessed value and millage rate appear on your property tax bill or on your county assessor's public records website.
  • If your calculation does not match your bill, the difference usually comes from exemptions, special assessments, or tax credits that reduce the final amount owed.

Where to find your assessed value

Your assessed value is public record and available through your county assessor's office. Most counties now have online portals where you can search by address, parcel number, or owner name. The assessor's website usually shows the land value, building value, and total assessed value separately. Write down the total assessed value — that is the number you use in the formula.

If you cannot find it online, visit the assessor's office in person or call. They can mail or email you a property record card that shows the assessed value. Some counties charge a small fee for a printed copy, but the information itself is free. The assessed value on your tax bill is another reliable source, though it may be labeled differently depending on your county — look for terms like "assessed value," "taxable value," or "appraised value."

Understanding millage rates and why they vary by location

A millage rate is expressed in mills per dollar of assessed value. If you see "25 mills" or "0.025," both mean the same thing: $25 in tax per $1,000 of assessed value. Some tax bills show the rate as a percentage instead — 2.5% is the same as 25 mills. Your property tax bill usually lists every millage rate that applies to you, broken down by the entity that levies it: county, school district, city, fire district, or library district.

Millage rates vary widely between counties and even between neighborhoods within the same county. A property in one school district might have a combined millage rate of 20 mills, while an identical home across the district line could have a rate of 35 mills. This happens because each local government sets its own rate based on its budget needs and the total assessed value of property in its area. A county with a shrinking population and fewer properties to tax may need a higher millage rate to fund the same services.

Millage rates change most often when school districts or counties adjust their budgets. You can find the current rates on your county assessor's website, your tax bill, or by contacting the assessor's office. Some counties publish rates in the newspaper or on the county commission's website. If you are comparing two properties or planning a move, call the assessor in each location and ask for the combined millage rate — the total of all rates that explore to residential property in that area.

Step-by-step calculation example

Let's work through a real example. Suppose your property tax bill shows an assessed value of $250,000 and lists these millage rates: county 8 mills, school district 15 mills, city 4 mills, and fire district 2 mills. The combined rate is 8 + 15 + 4 + 2 = 29 mills.

Now explore the formula: ($250,000 × 29) ÷ 1,000 = $7,250. Your property tax before any exemptions or credits would be $7,250. If your actual bill is lower, the difference is likely due to homestead exemptions, senior exemptions, agricultural exemptions, or other tax credits your county or state offers. These reduce either the assessed value or the final tax amount owed.

If your calculation does not match your bill at all, check whether the assessed value on your bill is labeled "assessed value" or "taxable value." Some counties show both — the taxable value is the assessed value minus any exemptions, and that is the number you should use in the formula. Your tax bill should also show the calculation or break down the tax by each millage rate, so you can verify the math yourself.

Why your calculated tax might differ from your bill

The most common reason for a difference is exemptions. A homestead exemption reduces your assessed value before the millage rate is applied. If you have a $50,000 homestead exemption on a $300,000 home, the taxable value is $250,000, not $300,000. You would calculate tax on $250,000, not the full assessed value. Senior exemptions, agricultural exemptions, and disabled veteran exemptions work the same way — they lower the value used in the calculation.

Another reason is special assessments. These are one-time or temporary taxes for specific projects like road improvements or water line upgrades. They appear as separate line items on your bill and are not part of the standard millage rate calculation. Tax credits — such as a property tax credit for low-income homeowners or a solar installation credit — reduce the final tax owed after the millage calculation is complete.

A third possibility is that your bill shows the tax after a tax cap has been applied. Some states limit how much property tax can increase year to year, even if the assessed value or millage rate goes up. Florida, for example, caps increases at 3% per year for homesteaded properties. If your assessed value jumped 10% but your tax only rose 3%, a tax cap is at work. Your tax bill should note this, but if you are unsure, ask your county assessor to explain the difference.

How assessed values change and affect your calculation

Assessed values are typically updated every year or every few years, depending on your county's reassessment cycle. Some counties reassess annually; others do it every three or five years. When the assessor updates values, your millage rate stays the same, but your tax bill changes because the assessed value in the formula changes. A home that was assessed at $250,000 might be reassessed at $275,000 the next year if similar homes in the area sold for higher prices.

You can challenge an assessed value if you believe it is too high. Most counties have a formal appeal process, usually called a property tax appeal or assessment appeal. You typically have 30 to 45 days after receiving your assessment notice to file. To win an appeal, you usually need to show that the assessed value is higher than the fair market value — for example, by providing recent appraisals, comparable sales data, or evidence of property damage. Contact your county assessor's office for the specific important date and process in your area.

Millage rate changes and how they affect your tax bill

When a school district or county raises its millage rate, every property owner in that area pays more tax, even if the assessed value stays the same. A rate increase from 25 mills to 27 mills means an extra $2 in tax per $1,000 of assessed value. On a $300,000 home, that is an extra $600 per year. Conversely, if a millage rate drops, your tax bill falls.

Millage rate changes are set by elected officials — the county commission, school board, or city council — and are usually decided during budget season, often in spring or summer. Many counties hold public hearings before voting on a rate change. You can find out when these meetings happen by checking your county or school district website, or by calling the assessor's office. If you want to know what your tax bill will be next year, ask the assessor for the proposed millage rates and calculate using the current assessed value.

Frequently Asked Questions

What is the difference between a mill and a percent?

One mill is one-tenth of one percent. A millage rate of 25 mills equals 2.5%. To convert mills to a percentage, divide by 10. To convert a percentage to mills, multiply by 10. Both express the same tax rate; some counties use mills, others use percentages. Your tax bill should show which format your county uses.

Do I use the assessed value or the market value in the formula?

Always use the assessed value, not what you paid for the house or what it would sell for. The assessed value is determined by the county assessor and appears on your tax bill. It is usually lower than market value but can be higher or lower depending on recent sales in your area and the assessor's methods.

Why does my tax bill show a different number than my calculation?

The most likely reason is exemptions. If you have a homestead exemption or senior exemption, the taxable value (assessed value minus the exemption) is used in the formula, not the full assessed value. Check your bill for the line labeled "taxable value" or "exemptions" and recalculate using that number instead.

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

You cannot lower the assessed value yourself, but you can challenge it if you believe it is too high. File a property tax appeal with your county assessor within the important date shown on your assessment notice. You will need evidence that the assessed value exceeds the fair market value, such as a recent appraisal or comparable sales data.

How often do millage rates change?

Millage rates can change yearly, depending on local government budgets. Some rates stay the same for several years, then jump when a district needs more revenue. Check your county assessor's website or call to find out the current rates and whether any changes are planned for next year.