How property tax is calculated where you live

Property tax is calculated by multiplying your home's assessed value by the tax rate set by your local government. The assessed value is not what you paid for the house or what it would sell for today — it is a value assigned by your county or township assessor, usually lower than market value. The tax rate, called the millage rate or mill rate, is expressed as dollars per $1,000 of assessed value and varies by county, school district, and municipality.

The basic formula is: Assessed Value × (Mill Rate ÷ 1,000) = Annual Property Tax. For example, if your home is assessed at $250,000 and your mill rate is 15 mills (or 15 per $1,000), your calculation would be $250,000 × (15 ÷ 1,000) = $3,750 per year. However, most homeowners do not do this math themselves — your tax bill arrives in the mail from your county assessor's office, and the calculation is already done.

Key Takeaways

  • Your property tax bill is based on your home's assessed value (set by the county assessor) multiplied by your local mill rate (set by your county, school district, and other local bodies).
  • The mill rate varies significantly by location and can change year to year, so two identical homes in different counties can have very different tax bills.
  • You can find your assessed value and mill rate on your tax bill, your county assessor's website, or by calling the assessor's office directly.
  • Homestead exemptions, senior exemptions, and other local programs can reduce your assessed value and lower your tax bill if you meet the requirements.
  • If you believe your assessed value is too high, you can file a formal challenge called an appeal or grievance, usually within 30 days of receiving your bill.

Where to find your assessed value

Your assessed value appears on your property tax bill, which your county assessor mails to you once or twice per year depending on your state. The bill also shows the mill rate and the calculation. If you have lost your bill or want to check the value before the bill arrives, you can look it up online through your county assessor's website — most counties now post assessment data publicly.

To find your county assessor's website, search "[your county name] assessor" or "[your county name] property records." You will typically enter your address or parcel number to pull up your property card, which shows the assessed value, the land value, the building value, and sometimes the year of last assessment. If you cannot find it online or prefer to speak with someone, call your county assessor's office and ask for your current assessed value. They can also tell you when your property was last reassessed and whether a new assessment is scheduled.

Understanding mill rates and where they come from

The mill rate is set by multiple local bodies — your county government, school district, city or village, and sometimes special districts like fire protection or library districts. Each body sets its own portion of the rate, and they add together to create your total mill rate. A mill rate of 20 mills means you pay $20 in property tax per $1,000 of assessed value per year.

Mill rates change annually because local governments adjust their budgets and tax revenue needs. A school district might raise its portion of the rate if enrollment increases, or a county might lower its portion if it receives state funding. You can find the breakdown of your mill rate on your tax bill or by asking your county assessor or school district office. Some counties publish the mill rate history for the past several years, which helps you see whether your rate is rising or stable.

How exemptions reduce your assessed value

Many states and counties offer exemptions that lower your assessed value, which directly lowers your tax bill. The most common is the homestead exemption, which reduces the assessed value for owner-occupied homes. The amount varies widely — some states reduce it by a flat dollar amount (for example, $50,000), while others reduce it by a percentage (for example, 20 percent). To receive a homestead exemption, you must own the home and live in it as your primary residence.

Other exemptions include those for seniors, veterans, people with disabilities, and agricultural land. Each state and county sets its own rules about who qualifies and how much the exemption is worth. You typically file for an exemption once with your county assessor, and it renews automatically each year unless your circumstances change. If you think you may may have access to for an exemption, contact your county assessor's office and ask what programs are available in your area and what documents you need to provide.

What happens if you think your assessed value is wrong

If you believe your assessed value is too high, you can file a formal challenge. The process and timeline vary by state, but it usually begins with a document called a grievance, appeal, or assessment challenge. Most counties require you to file within 30 days of receiving your tax bill, though some allow longer. You file with your county assessor's office, not with the tax collector.

When you file, you typically must explain why you think the value is wrong — for example, your home needs major repairs, comparable homes in your area sold for less, or the assessor made a factual error about the property. You may need to provide evidence such as a recent appraisal, a list of comparable sales, or photos of damage. The assessor will review your challenge and either agree and lower the value, or disagree and uphold it. If you disagree with their decision, most states allow a second appeal to a county board or to tax court, though this usually requires a lawyer and costs money.

How to estimate your tax bill before it arrives

If you know your assessed value and your mill rate, you can calculate your estimated tax bill using the formula: Assessed Value × (Mill Rate ÷ 1,000) = Annual Tax. For example, a $300,000 assessed value with an 18-mill rate would be $300,000 × (18 ÷ 1,000) = $5,400 per year.

To find your mill rate before your bill arrives, check your previous year's tax bill or call your county assessor's office. They can tell you the current year's rate, though it may not be final until the local government budgets are approved (usually in late summer or early fall). Keep in mind that if your home was recently reassessed, your assessed value may have changed, which would change your bill even if the mill rate stays the same. Your county assessor can tell you whether a reassessment is scheduled for your property.

Frequently Asked Questions

Is the assessed value the same as what I paid for my house?

No. The assessed value is set by the county assessor and is usually lower than the purchase price. It is based on the assessor's estimate of the home's market value, but it lags behind actual market changes. Some states reassess every year, while others reassess every three to five years, so the assessed value may be outdated compared to current market conditions.

Can my property tax bill go down if my home loses value?

Yes, but only if your county reassesses and the assessor lowers your assessed value. If your area experiences a housing market decline, the assessor may lower values during the next reassessment cycle. You can also file an appeal if you believe your current assessed value is too high. However, if your county does not reassess frequently, your value may not adjust downward even if the market falls.

What is the difference between assessed value and appraised value?

An appraised value is an estimate done by a licensed appraiser, usually for a bank during a mortgage or refinance. An assessed value is set by the county assessor for tax purposes. They are often different — the appraised value is usually closer to the current market price, while the assessed value may be lower and may not reflect recent market changes.

Do I have to pay property tax if I own my home outright?

Yes. Property tax is owed by the owner of the property, whether the home is paid off or financed. If you have a mortgage, your lender may collect property tax as part of your monthly payment and pay it on your behalf, but you are still legally responsible for it. If you own the home outright, you receive the bill directly and must pay it yourself.

How often does the assessed value change?

This depends on your state and county. Some counties reassess every year, while others reassess every three to five years or only when the property changes hands. You can find out your county's reassessment schedule by calling the assessor's office or checking their website. Even in years when there is no formal reassessment, the assessor may adjust values if they discover a factual error, such as an incorrect square footage or number of bedrooms.