What does mill rate mean and how does it affect your tax bill

Last updated 2026-07-09

What is a mill rate in property taxes?

A mill rate is a tax rate expressed in units called mills, where one mill equals one-tenth of one cent, or $0.001. In plain English, one mill of tax on a $1,000 assessed value produces exactly $1.00 in tax. So when your county assessor's office reports a combined mill rate of, say, 32.5, that means you owe $32.50 for every $1,000 of assessed value on your property. ^[1]

The word 'mill' comes from the Latin 'millesimum,' meaning one-thousandth. Local governments have used millage as the standard unit for property tax rates in most U.S. states for over a century, because it lets a single number describe a rate without a string of decimal places. Some states, including Georgia and Michigan, use the term 'millage rate' in their statutes by name. ^[2]

You'll sometimes see mill rates written as a decimal multiplied against the full assessed value instead of per $1,000. The math is identical. A mill rate of 20 equals a tax rate of 0.020, or 2.0 percent of assessed value. Both expressions produce the same bill.

The mill rate on your notice is almost never a single number from a single government. It's a composite. Your county levies mills. Your municipality levies mills. Your school district, fire district, library district, and community college district each levy mills. The number on your bill is the sum of all of them. That sum is called the total combined millage or the total levy rate. ^[1]

How do you calculate property tax from a mill rate?

The formula is short:

Property Tax = (Assessed Value / 1,000) × Mill Rate

Or equivalently:

Property Tax = Assessed Value × (Mill Rate / 1,000)

Work through a real example. Say your county sets a total combined mill rate of 28.4 mills and your property's assessed value is $260,000.

$260,000 ÷ 1,000 = $260 $260 × 28.4 = $7,384 in gross tax before exemptions.

If you qualify for a homestead exemption that reduces your assessed value by $50,000, you'd pay tax on $210,000 instead: $210,000 ÷ 1,000 = $210 $210 × 28.4 = $5,964.

That $1,420 difference comes entirely from the exemption, not from any change in the mill rate. ^[3]

One thing trips people up. Many states apply the mill rate not to market value but to assessed value, which may be a fraction of market value. In California, Proposition 13 limits assessed value and the general levy to 1 percent of assessed value (essentially 10 mills), but local bonds and special assessments are added on top. ^[4] In Ohio, a 'reduced millage' system means effective rates are often roughly half the voted millage on paper, because the state applies a 10-mill floor and rollbacks. So always start with the number on your actual tax bill rather than a headline mill rate figure you find online.

How is the mill rate set each year?

Every taxing district, whether it's a county, school board, or fire authority, runs a budget cycle. The governing body estimates how much revenue it needs for the coming year. It then divides that revenue need by the total assessed value of all taxable property in the district to arrive at a mill rate that will produce exactly that revenue. ^[1]

The formula from the government side looks like this:

Mill Rate = (Total Revenue Needed × 1,000) / Total Assessed Value of All Taxable Property

This is why mill rates can fall even when governments spend more money. If assessed values rise fast enough, the same revenue need produces a lower mill rate. Florida's 'Truth in Millage' (TRIM) law, codified in Florida Statutes Section 200.065, requires local governments to publicly advertise and hold hearings whenever they plan to adopt a millage rate higher than the rolled-back rate, the rate that would produce the same total revenue as the prior year given new assessments. ^[5] Many states have similar truth-in-taxation or rollback rate laws. Texas calls its version the 'no-new-revenue rate' under Tax Code Section 26.04. ^[6]

Once a mill rate is adopted at a public hearing and certified, it's fixed for that tax year. Individual property owners have no mechanism to challenge the rate itself. What you can challenge is the assessed value it gets multiplied against. That's why an inflated assessment is a direct money problem. Every extra $10,000 in assessed value costs you an extra $10 per mill in annual taxes, year after year.

What is a good or bad mill rate, and how do rates compare across the U.S.?

There's no universally 'good' mill rate, because mill rates mean nothing without the assessment ratio, the exemptions available, and what services those mills fund. A New Jersey township might levy 70 mills but apply them to an assessed value that's 100 percent of market value with no broad exemptions, producing some of the highest effective tax rates in the country. A Louisiana parish might show 150 mills but apply them to an assessed value that's only 10 percent of market value for residential property, producing a very low effective bill. ^[7]

The more useful comparison is effective tax rate: annual tax paid divided by market value. The Lincoln Institute of Land Policy and Minnesota Center for Fiscal Excellence publish a 50-state survey of effective rates every year. Their 2023 data found median owner-occupied effective rates ranging from about 0.28 percent in Hawaii to about 2.23 percent in Illinois. ^[7]

State	Approx. effective rate (2023)	Notes
Hawaii	0.28%	Very low assessment ratios
Alabama	0.41%	10% assessment ratio for residential
Colorado	0.51%	Gallagher-era caps; changed after 2020
Texas	1.60%	No income tax; schools funded by property tax
Illinois	2.23%	Highest in Lincoln Institute 2023 survey
New Jersey	2.13%	Full-value assessment, high school levies

Source: Lincoln Institute of Land Policy, '50-State Property Tax Comparison Study,' 2023 ^[7]

Your own effective rate is the number that matters. Divide your annual tax bill by your home's market value. If that percentage runs higher than neighbors with similar homes, you may have an assessment problem worth appealing, regardless of what the nominal mill rate says.

What is the difference between mill rate and assessment ratio?

These two numbers work together to set your real tax burden, and confusing them is one of the most common mistakes homeowners make when comparing tax bills.

The mill rate is set by government budgets. The assessment ratio is a policy choice about what fraction of a property's market value gets taxed. Many states deliberately assess residential property at less than full market value. Alabama, for example, sets its residential assessment ratio at 10 percent under state law, so a $300,000 home has a $30,000 assessed value, and even a high mill rate produces a modest bill. ^[8]

In states that assess at full market value (100 percent ratio), the mill rate directly reflects the tax burden. In states with low ratios, published mill rates can look alarmingly high while the actual bill is quite low.

Here's how the two combine:

Effective Tax Rate = (Mill Rate / 1,000) × Assessment Ratio

So a mill rate of 100 mills combined with a 10 percent assessment ratio produces the same effective rate as a mill rate of 10 mills with a 100 percent assessment ratio. Both equal 1.0 percent of market value.

Your county assessor's website should publish the current assessment ratio. If it doesn't, the state department of revenue or state auditor typically does. Look for terms like 'assessment level,' 'equalization ratio,' or 'common level of assessment.' ^[3]

Does a higher mill rate mean you should appeal your assessment?

A higher mill rate amplifies the cost of any over-assessment. That's the direct connection. If your property is assessed $30,000 too high and the mill rate is 10 mills, you're overpaying $300 a year. At 30 mills, that same $30,000 over-assessment costs you $900 a year. At 50 mills, $1,500. Every mill matters when the assessed value is wrong. ^[1]

The mill rate itself is not appealable. Your local government sets it through a public budget process, and as a property owner you can attend those hearings and object, but there is no administrative appeal of a mill rate the way there is for an assessment. What you can appeal is the assessed value of your specific property, and a high mill rate is one of the best reasons to make sure that number is accurate.

The two grounds most commonly accepted in assessment appeals are: (1) the assessment exceeds market value, meaning the assessor overestimated what your property would sell for, and (2) the assessment is unequal, meaning your property is assessed at a higher ratio to market value than comparable properties nearby. ^[9]

If you're in a high-mill-rate jurisdiction and your assessment looks even slightly elevated, the math on appealing is almost always favorable. For many homeowners in Cook County, Illinois (where combined mill rates in some townships exceed 10 percent of assessed value, with a 10 percent assessment ratio), a successful appeal can recover hundreds to thousands of dollars per year. [See how Cook County bills work at /articles/appeal-process/cook-county-tax-assessor-tax-bill.]

Before you hire anyone, check whether a DIY appeal makes sense. A structured process like the TaxFightBack appeal kit walks you through gathering comparables and filing the forms yourself, so the full savings stay in your pocket.

How do you find your property's current mill rate?

Four reliable places to look:

1. Your property tax bill or tax notice. Almost every county includes a breakdown of millage by taxing district. Look for a table labeled something like 'tax district,' 'levy,' or 'millage breakdown.' The total at the bottom is your combined mill rate for that year.

2. Your county assessor or county auditor website. Many post the current certified mill rate tables or levy sheets as PDFs. Search 'your county name millage rate' or 'levy sheet' plus the current year.

3. Your state department of revenue. States that certify mill rates centrally, like Georgia's Department of Revenue or Ohio's Department of Taxation, publish mill rate tables by county and district that are updated annually. ^[2]

4. Your local government's budget documents. School boards and county commissions are required in most states to publish proposed and adopted mill rates as part of their public budget hearings.

If you're a homeowner in Maricopa County, Arizona, the county treasurer publishes combined tax rates by tax area code each year at the county treasurer's website. [See the full picture for Maricopa at /articles/appeal-process/maricopa-property-tax.] Residents in San Diego can find their rate area information through the county auditor-controller's office. [/articles/appeal-process/san-diego-property-tax]

One caution: rates published mid-year may be preliminary. The certified rate, the one actually applied to your bill, is the final number after all budgets are adopted and the state auditor or equivalent office approves them.

How do special assessments and bond levies affect the mill rate?

Your combined mill rate almost certainly includes several line items you've never thought about. The 'general fund' levy from your county and city covers day-to-day services like roads and administration. Separate from that are voted bond levies, special tax district levies, and assessment district charges.

Voted bond levies are exactly what they sound like. Voters approved a bond measure (a school construction project, a stadium, a transit line), and the debt service on those bonds is collected as additional mills on everyone's tax bill in the district. These are typically listed as a separate millage line on your bill. ^[1]

Special assessment districts, like a local improvement district for new sidewalks, or a community facilities district for infrastructure in a new subdivision, can add flat dollar charges that aren't expressed as mills but appear on the same bill. These are not part of the mill rate. They're fixed charges, and they're often not appealable through the standard assessment appeal process, though some states have separate procedures for challenging special assessments.

In California, because Proposition 13 capped the general levy at 1 percent (10 mills), nearly all the variability in California property tax bills comes from these voter-approved debt service levies stacked on top. A Los Angeles homeowner might have a general levy of 1 percent plus another 0.3 to 0.5 percent in bond and Mello-Roos district charges, making the effective rate meaningfully higher than the 1 percent cap suggests. [/articles/appeal-process/los-angeles-county-property-tax]

The practical point: when you compare your bill to a neighbor's or to published rates, make sure you're comparing the same components, more than just the base general levy.

Can the mill rate change after your assessment is set?

Yes. Mill rates and assessments run on separate timelines in most states.

Your assessed value is typically set once a year, or on a cycle of every two to four years depending on the state, as of a specific assessment date. But the mill rate is set after budgets are finalized, usually later in the year. In Georgia, assessments are set earlier in the year and mill rates are adopted by local governments by the end of the fiscal year. ^[2] In Texas, appraisals are certified by July 25 and tax rates must be adopted by the governing bodies under deadlines set in Tax Code Section 26.05. ^[6]

This means you can do everything right in an assessment appeal and still see your bill change because the mill rate moved. If assessed values across the entire county rise uniformly (say, a 10 percent mass reassessment), many local governments lower the mill rate proportionally to collect the same total revenue, holding most homeowners' bills flat. But if only your neighborhood got reassessed upward while others didn't, you're paying more mills on a higher base without any offset.

This is one of the arguments for appealing an assessment even in a low-mill-rate year. Once the assessor's record shows an inflated value, that number is the starting point for all future years until you correct it.

How does understanding the mill rate help you appeal your assessment?

Knowing the mill rate converts an abstract complaint ('my assessment seems high') into a precise dollar figure ('my assessment is $40,000 too high, which costs me exactly $1,120 per year at the current 28-mill combined rate'). That precision matters for two reasons.

First, it tells you whether the appeal is worth your time. Most jurisdictions have filing fees ranging from zero to around $30 to $50. A serious DIY appeal usually takes four to eight hours. If the math says a successful appeal saves $200 a year, that's an easy call. If the over-assessment is only $5,000 in a 10-mill county (a $50 per year difference), you might pass.

Second, it strengthens your case on paper. When you file an appeal and include a cover letter that says 'at the current mill rate of 28.4 mills, this $40,000 overassessment has cost me $1,136 per year and I request a corrected assessment of $X based on the comparable sales attached,' you signal to the review board that you understand the system. Boards hear a lot of vague complaints. Precise math stands out.

For homeowners in Georgia counties like Gwinnett, the appeal period opens after assessment notices go out, typically in the spring, and runs 45 days from the date of the notice. [/articles/appeal-process/gwinnett-county-tax-assessor] In Bexar County, Texas, the deadline to protest is May 15 or 30 days after the appraisal notice is mailed, whichever is later. [/articles/appeal-process/bexar-county-tax-assessor] Miss that window and you pay the full bill for another year, so the mill rate math earns its keep when you do it early.

The TaxFightBack appeal kit includes a worksheet that applies your local mill rate to the comparable sales you find, so you can walk into any hearing with a precise savings number already calculated.

What are mill rates in different states actually called?

The terminology varies enough to cause real confusion when you're researching your own bill.

'Mill rate' and 'millage rate': used in Connecticut, Georgia, Michigan, Pennsylvania, and many Midwestern states. Georgia's Department of Revenue uses 'millage rate' throughout its property tax guidance. ^[2]

'Tax rate': the generic term used in most states, expressed as a dollar amount per $100 or per $1,000 of assessed value. Texas tax rate tables are published as dollars per $100 of value, so a Texas rate of $1.20 per $100 equals 12 mills. ^[6]

'Levy rate': common in Washington state, where the Department of Revenue publishes levy rate tables by taxing district. ^[3]

'Ad valorem rate': the Latin term ('according to value') appears in state statutes in Florida, Georgia, and Texas, among others. All property taxes based on assessed value are technically ad valorem taxes, and the mill rate is how that ad valorem rate is expressed. ^[5]

'Tax area code' or 'rate area': administrative codes used in California and Arizona to group parcels that share the same combination of taxing districts, making it easier to look up the combined rate for any given address. ^[4]

Whatever it's called, the underlying math is the same. Find the rate expressed per $1,000 (or convert it), multiply it against the taxable assessed value, subtract any exemption credits, and you have your gross tax.

If you're researching a specific county, like Madison County or Lake County, the assessor or auditor website is almost always the fastest path to the right number for the right year.

What should you do if your mill rate seems unusually high compared to nearby counties?

First, confirm you're comparing the same thing. A neighboring county with a lower mill rate might assess property at 100 percent of market value while yours assesses at 40 percent, making the apparent difference meaningless on a dollar-for-dollar basis. Always convert to effective rate (tax paid / market value) before drawing any conclusions.

If the effective rate genuinely is higher in your jurisdiction, there are a few likely explanations. School district spending is by far the biggest driver of high total millage in most parts of the country: the Lincoln Institute found that school levies account for roughly 40 to 50 percent of the average residential property tax bill nationwide. ^[7] Fragmented local government, many small overlapping taxing districts each levying a few mills, also tends to push combined rates up. New Jersey's famously high effective rates partly reflect its dense layering of municipal, county, and school levies.

As an individual property owner, you can't fix the mill rate. What you can do: verify your assessed value is accurate, claim every exemption you qualify for (homestead, senior, veteran, disability, agricultural, and others depending on your state), and if your effective rate runs high relative to neighbors with comparable properties, file a formal assessment appeal.

For homeowners in St. Louis County or Cherokee County, Georgia, the combination of state-specific assessment rules and local mill rates can make the math feel opaque, but the underlying process is the same everywhere: get the assessed value right, and every mill on the rate works in your favor rather than against you.

Frequently asked questions

What does one mill equal in dollars?

One mill equals $1 of tax per $1,000 of assessed value. So if your assessed value is $200,000 and your total mill rate is 25, your gross tax before exemptions is $200,000 divided by 1,000, times 25, which equals $5,000. Every additional mill on a $200,000 assessment costs you exactly $200 per year.

Is mill rate the same as tax rate?

They describe the same thing in different units. A mill rate of 20 equals a tax rate of 0.020 or 2.0 percent of assessed value. Some states express their rates per $100 rather than per $1,000. A Texas rate of $1.20 per $100 equals 12 mills. Convert by multiplying a per-$100 rate by 10 to get mills.

Can I appeal my mill rate if I think it's too high?

No. Mill rates are set through the government's public budget process, not through property assessment. You can attend public hearings when local governments adopt their budgets and speak on the record, but there is no formal administrative appeal of a mill rate. What you can appeal is your property's assessed value, which is the number the mill rate gets multiplied against.

How often does the mill rate change?

Most taxing districts recalculate and adopt a new mill rate every year as part of the annual budget process. The rate can go up, down, or hold flat depending on spending decisions and how total assessed values changed across the jurisdiction. A large countywide reassessment often causes the mill rate to drop, because the revenue need is spread across a bigger total assessed value base.

Does a lower mill rate mean lower property taxes?

Not necessarily. A lower mill rate can come with a higher assessment ratio, a higher total assessed value, or fewer exemptions, leaving your bill the same or higher. The only reliable measure of your tax burden is effective rate: your total annual tax bill divided by your property's current market value. That number is what you should compare across jurisdictions.

Where can I find my property's mill rate?

Check your property tax bill first. It usually includes a breakdown by taxing district. Your county assessor, county auditor, or county treasurer website should also publish the current certified mill rate table. Your state department of revenue often posts statewide tables by county. Search for your county name plus 'mill rate' or 'levy rate' and the current year.

What is a combined or composite mill rate?

It's the sum of all individual mill rates levied on your property by every overlapping taxing district: county, municipality, school district, fire district, and any special districts. Most property tax bills list each district separately and then show a total. That total is your combined or composite mill rate, and it's the number you use to calculate your full tax bill.

How does the assessment ratio affect what the mill rate actually costs me?

The assessment ratio sets the taxable base the mill rate is applied to. If your state assesses residential property at 40 percent of market value, a $400,000 home has an assessed value of $160,000. Multiply that by your mill rate, not the full market value. A 30-mill rate on $160,000 produces $4,800 in tax, not $12,000. Ignoring the ratio causes many homeowners to misread headline mill rates as catastrophically high.

What is the Truth in Millage (TRIM) notice in Florida?

Florida's Truth in Millage law, under Florida Statutes Section 200.065, requires county property appraisers to send every property owner a TRIM notice each August showing the proposed assessed value, proposed mill rates from each taxing authority, and the estimated tax bill. It also shows what the bill would be if each government adopted the rolled-back rate. The TRIM notice is the legal start of Florida's assessment appeal window, which is 25 days from the mailing date.

Do renters pay property taxes at the mill rate?

Renters don't receive a property tax bill directly, but landlords factor property taxes into rent pricing, so renters effectively bear part of the cost. Some states, like Minnesota and Michigan, have renter property tax refund or credit programs that acknowledge this. Those programs are separate from the mill rate itself and administered through state income tax returns.

How does a homestead exemption interact with the mill rate?

A homestead exemption reduces the assessed value before the mill rate is applied. If your assessed value is $250,000, you have a $50,000 homestead exemption, and the mill rate is 30 mills, you pay tax on $200,000: ($200,000 / 1,000) × 30 = $6,000. The higher the mill rate, the more a dollar of exempted value saves you, because each dollar cut from the base spares you more mills-worth of tax.

Is property tax the same as ad valorem tax?

Effectively yes for real property. 'Ad valorem' means 'according to value' in Latin, and all standard residential and commercial property taxes are ad valorem taxes, because they're calculated as a rate applied to assessed value. Some states also levy ad valorem taxes on personal property like vehicles and business equipment. The mill rate is the mechanism for calculating any ad valorem tax.

What causes mill rates to spike suddenly?

A sudden drop in total assessed values, like after a housing market crash, forces mill rates up if governments hold their spending steady. A large taxpayer leaving the tax roll, a failed referendum that forces a different funding mechanism, or a one-time debt obligation can also push rates up sharply in a single year. In small special districts, the loss of one big commercial property can move the mill rate a lot for all remaining owners.

How do I use the mill rate to decide if an appeal is worth filing?

Estimate your over-assessment in dollars. Multiply that number by your mill rate divided by 1,000. That's your annual overpayment. For example, a $25,000 over-assessment at 35 mills costs ($25,000 / 1,000) × 35 = $875 per year. If your appeal has a reasonable chance of success and the annual savings beat the time and any filing cost, the math almost always favors filing.

Sources

1. International Association of Assessing Officers (IAAO), Property Assessment Valuation: Definition of mill rate as $1 per $1,000 of assessed value; combined millage as sum of all overlapping taxing district levies
2. Washington State Department of Revenue, Property Tax Levy Guide: Assessment ratio and levy rate combine to calculate property tax liability; levy rate tables published by taxing district
3. California State Board of Equalization, Property Tax Rules: Proposition 13 caps general levy at 1 percent of assessed value; additional voter-approved bond levies added on top; tax rate areas used for combined rate lookup
4. Florida Department of Revenue, Truth in Millage (TRIM) Program, Florida Statutes Section 200.065: TRIM law requires local governments to advertise and hold hearings when adopting a millage rate above the rolled-back rate; TRIM notice mailed in August starts the 25-day appeal window
5. Texas Comptroller of Public Accounts, Property Tax Code Section 26.04 and 26.05: Texas no-new-revenue rate calculation; tax rates expressed per $100 of value; adoption deadline under Tax Code Section 26.05
6. Lincoln Institute of Land Policy and Minnesota Center for Fiscal Excellence, 50-State Property Tax Comparison Study, 2023: Median effective residential property tax rates by state ranging from approximately 0.28 percent in Hawaii to 2.23 percent in Illinois; school levies account for approximately 40 to 50 percent of average residential property tax bill nationwide
7. Alabama Department of Revenue, Property Tax, Residential Assessment Ratio: Alabama sets residential property assessment ratio at 10 percent of market value under state law
8. International Association of Assessing Officers (IAAO), Standard on Assessment Appeals: The two main grounds for assessment appeals are value exceeds market value and unequal assessment compared to comparable properties
9. Cook County Assessor's Office, Understanding Your Assessment: Cook County Illinois uses a 10 percent assessment ratio for residential property; combined mill rates in some townships produce effective rates that make assessment accuracy financially significant
10. Maricopa County Treasurer, Tax Rate Tables: Maricopa County Arizona publishes combined tax rates by tax area code annually on the county treasurer website