How do mill rates work and what they mean for your tax bill

Last updated 2026-07-09

What is a mill rate and where does the word 'mill' come from?

A mill is one-thousandth of a dollar. The word comes from the Latin "millesimum," meaning thousandth. A mill rate of 20 means you pay $20 for every $1,000 of assessed value, or exactly two cents on the dollar. That's the whole idea.

The rate travels under different names. You'll see "millage rate" on bills in Georgia, Alabama, and most of the South. Texas calls it a "tax rate" and expresses it per $100 of value instead of per $1,000 (confusing, but mathematically the same, just divided differently). Ohio, Michigan, and Illinois lean toward "mill levy." Colorado statutes use "mill levy" too and write it as a decimal like 0.05000. Different words, identical math.

The term sticks around because it drops cleanly into the arithmetic assessors run. One mill on a $200,000 assessed home produces exactly $200 in tax. That tidy relationship makes the rate easy to announce, vote on, and explain, even though almost nobody outside a county office says the word "mill" in daily life.

How do you calculate property tax using the mill rate?

Three variables, one line of arithmetic. Assessed Value x Mill Rate / 1,000 = Annual Tax. That's it.

Assessed Value x Mill Rate / 1,000 = Annual Tax

Here's a real example. Your home has a market value of $350,000. Your county assesses at 40% of market value (called the assessment ratio), so your assessed value is $140,000. The combined mill rate for your taxing district is 32 mills.

$140,000 x 32 / 1,000 = $4,480 per year

Now watch what happens when the county over-assesses your home at $380,000 instead of $350,000. The assessed value becomes $152,000 and the tax jumps to $4,864. That's $384 a year gone, every year, until you fix it. That single gap is why a bad assessment is worth appealing even in a place people call "low mill rate."

Some states skip the ratio step by assessing at 100% of market value. There, assessed value equals market value and you drop the ratio multiplication. Illinois runs different ratios by county (Champaign County targets 33.3%; Cook County residential targets 10% ^[1]), which makes comparing mill rates between two Illinois counties close to meaningless unless you also know each ratio.

Texas quotes its rate per $100, not per $1,000, so you'll see numbers like $1.20 per $100. Multiply by 10 to convert to mills. A Texas rate of $1.20 per $100 is 12 mills. ^[2]

What is a combined or composite mill rate?

No single government sets the number on your bill. Several taxing districts each add a levy to the same property, and the county treasurer sums them into one figure. A typical homeowner is quietly paying into:

• The county general fund
• The municipal or township government
• One or more school districts (usually the biggest slice)
• A community college district
• A fire protection district
• A library district
• A special assessment district (roads, drainage, or parks)

In Maricopa County, Arizona, the Maricopa County Assessor's office publishes a breakdown that lists individual levies from the county, cities, school districts, and community colleges, all combined into one rate against assessed value. ^[3] The same structure shows up in Cook County, where the Cook County tax assessor posts each taxing district's levy separately before rolling them together.

This matters because each slice answers to a different political process. Cutting the county's levy takes the county board. Cutting the school levy takes the school board, often with a voter referendum on top. You can't personally vote any of them down. But you can go after the one input every levy shares: your assessed value. Knock 10% off the assessment and you cut all of those levies by 10% at once.

What are typical mill rates across U.S. states?

Mill rates swing so widely that a neighbor's rate in another state tells you almost nothing. States that assess close to full market value tend to post lower nominal mill rates. States with low assessment ratios post higher nominal rates to raise the same money. The real burden depends on both numbers together, never one alone.

The Lincoln Institute of Land Policy tracks effective tax rates (total tax as a percentage of market value) across major U.S. cities every year. Its 2023 "50-State Property Tax Comparison Study" found effective rates running from roughly 0.28% in Hawaii to about 2.47% in Illinois, with the national median near 1.0% of market value. ^[4]

State	Typical combined mill rate range	Assessment ratio	Notes
New Jersey	15 to 35 mills	~100% market value	Highest effective rates in U.S.
Illinois	5 to 9 mills in Cook Co.	10% residential	Low mills, low ratio, high effective rate
Georgia	25 to 45 mills	40% of fair market value	School mills dominate
Texas	1.0 to 2.5 per $100 (10 to 25 mills)	100% market value	No state income tax
California	~10 mills base	100% AV	Prop 13 caps at 1% + voter debt
Ohio	20 to 70 mills	35% of true value	Wide range by district
Colorado	5 to 50 mills	Varies by property class	Assessed value reset every 2 years

Sources: Lincoln Institute 2023 ^[4], state statutes cited below.

California's Proposition 13 deserves its own flag. It caps the base tax rate at 1% of assessed value (about 10 mills) and limits annual assessment increases to 2% until the property sells. ^[5] That's why two identical homes on one California street can carry wildly different bills. The mill rate is nearly uniform. The assessed values drift apart year after year.

In Georgia, the Gwinnett County Tax Assessor and the Bexar County Tax Assessor in Texas both post their combined rates in public. You still can't compare the two numbers head to head without knowing each county's assessment ratio.

How do local governments set the mill rate each year?

Mill rates aren't carved in stone. Local governments recompute them every budget cycle, usually once a year. The process runs backward from the budget, not forward from your house.

The school board or county commission first decides how much revenue it needs. It divides that revenue target by the total assessed value of all taxable property in the district. The result is the mill rate required to hit the budget.

Mill Rate = Total Tax Revenue Needed / (Total Assessed Value / 1,000)

Reassessment years are where this gets tricky. If a county revalues everything and assessed values jump 20% on average, the rate needed to collect the same total revenue drops by roughly 17%. Whether the government actually rolls the rate back or keeps it flat (a quiet tax increase) is a political choice, not a mathematical one. Many states have "rollback rate" laws that force the government to at least notify taxpayers or hold a public vote before collecting more than last year's revenue. Texas's Truth-in-Taxation law tells jurisdictions to publish a "no-new-revenue rate" and hold a public hearing if they plan to exceed it. ^[6]

So even when the mill rate holds steady, your bill can climb if your assessment climbs. Flip it around: in a falling market, if the government keeps the rate flat while values drop, revenue falls and services get squeezed. Neither result says much about what your house is truly worth. It's the government balancing a budget.

What is the difference between nominal mill rate and effective tax rate?

The nominal mill rate is the number printed on your bill. The effective tax rate is total tax paid divided by actual market value. For the same house, those two numbers can look nothing alike.

Here's why. In a county that assesses at 30% of market value with a 50-mill rate, the nominal rate is 50 mills but the effective rate is 50 x 0.30 / 1,000 = 1.5% of market value. In a county that assesses at 100% with a 12-mill rate, the nominal rate looks tiny while the effective rate is 1.2%, nearly the same burden.

For comparing taxes across counties or states, effective rate is the only honest number. The Lincoln Institute study uses effective rates for exactly this reason. Its 2023 data show the 10 highest-rate cities (led by Detroit and Milwaukee) carried effective rates two to four times those of the 10 lowest-rate cities (led by Honolulu and Denver). ^[4]

For your own appeal, the nominal mill rate becomes useful in reverse. It tells you how much each $1,000 of assessment reduction saves you. A 40-mill combined rate means every $1,000 you knock off saves $40 a year. On a $50,000 over-assessment, that's $2,000 a year in permanent savings. If you're weighing whether to file, and pages like san diego property tax or lake county property tax show your effective rate, run the math: over-assessment in dollars x mill rate / 1,000 = your annual overpayment.

Can you fight the mill rate itself or only your assessed value?

You can't change the mill rate on your own. It's set through a public legislative process, almost always by an elected board. Fighting it means showing up at budget hearings, organizing other taxpayers, or electing different board members. None of that lands before your next bill is due.

Your real lever is assessed value. Appealing an over-assessment is the one move an individual homeowner can make that cuts the tax right away (or retroactively if you win after paying), with no wait for the politics to shift.

The process varies by county. Most require a written appeal within 30 to 90 days of your assessment notice. Many run a formal hearing board: Bexar County uses the Appraisal Review Board ^[7], Georgia counties use the Board of Equalization, and Cook County uses the Board of Review. ^[1]

If you'd rather do this yourself, the TaxFightBack DIY appeal kit walks you through pulling comparable sales, writing your protest letter, and presenting at a hearing. You keep 100% of any reduction instead of handing a third of it to a contingency firm.

A handful of states do let taxpayers challenge the mill rate itself when it was set without the required procedures, like a skipped public hearing. Those legal fights are rare, expensive, and slow. The assessed-value appeal is almost always the right first move.

How do exemptions reduce the effect of the mill rate?

Exemptions carve a fixed dollar amount off assessed value before the mill rate touches it. A $25,000 homestead exemption at a 30-mill rate saves exactly $750 a year (25 x 30 = $750). The rate never changes. The base it hits gets smaller.

The exemptions that blunt the mill rate the most:

Homestead exemptions: Georgia offers a basic $2,000 state homestead exemption, and counties stack their own on top. Fulton County's total homestead exemption can reach $30,000 or more depending on the district. ^[8]

Senior or elderly exemptions: Many counties freeze assessed value or grant large flat exemptions to homeowners over 65. In Madison County, Alabama and Cherokee County, Georgia, senior exemptions can wipe out most of the school millage.

Disability exemptions: Veterans with service-connected disabilities get sizable exemptions in most states. Texas gives a 100% exemption to veterans rated 100% disabled. ^[9]

Agricultural-use value: In Coweta County and other Georgia counties, land assessed under current-use (agricultural) rules is valued far below market, which shrinks the base before the mill rate applies.

If you're not claiming every exemption you qualify for, you're overpaying no matter what the mill rate or your assessed value is. Check your county assessor's exemption list every year. Eligibility rules and application deadlines move around.

Why did my tax bill go up even though the mill rate didn't change?

This is the confusion homeowners bring to appeals more than any other. The rate held flat and the bill still jumped. What happened?

When the mill rate stays put but your assessed value rises, your bill rises in exact proportion. A 15% jump in assessed value on a home with a flat 30-mill rate produces a 15% higher bill. The rate is innocent. The assessment did it.

Several things push assessed value up with no change to your actual property:

• A county-wide reassessment built on new comparable sales from a hot market year
• A neighboring property selling high, which the assessor reads as evidence of your value too
• New construction or improvements pulled from permit data (sometimes logged in error, or a neighbor's permit coded to your parcel)
• A dropped exemption you forgot to re-certify

That third one catches a lot of people. In Bibb County, Georgia and plenty of other places, assessors pull building permit data every year. If a permit for any address on your block gets coded to your parcel by mistake, your assessment can jump thousands of dollars for work you never did. Always match the square footage and property characteristics on your notice against what's really on your lot.

The increase that stings worst arrives 12 to 18 months after a hot market. Assessors are legally required to value at market, so a market that ran up hard in 2021 to 2022 produced reassessment notices in 2022 to 2023 that shocked homeowners who never planned to sell. Your right to appeal doesn't vanish just because the market moved. It means you need recent comparable sales that support a lower value, including any softening that happened after the assessor's valuation date.

How do mill rates work for commercial property compared to residential?

The mill rate itself usually doesn't split between commercial and residential property in the same taxing district. It's one number applied to all taxable property. What differs is the assessment ratio and, in some states, the property class.

Several states run split-roll or classified systems. Minnesota uses different "class rates": homestead residential (a 1.0% class rate on the first $500,000 of value), commercial/industrial (1.5%), and apartment property (1.25%) before the mill rate applies. ^[10] Illinois reaches a similar split by assigning different assessment ratios, commercial at 25% in Cook County versus residential at 10%.

For commercial owners in places like St. Louis County, the calculation is identical but the stakes run higher, because commercial properties sit at higher ratios and carry bigger dollar values. A 5% over-assessment on a $5 million office building at a 30-mill rate is a $7,500 annual overpayment. Commercial appeals often head to a State Tax Commission or Superior Court instead of the local board of equalization, and they almost always need an MAI appraisal as evidence.

For Los Angeles County property tax purposes, commercial property under Proposition 13 gets the same 1% base cap plus voter-approved debt. Because commercial properties change hands less often than homes, many have been held at artificially low assessed values for decades.

How to use the mill rate to figure out if an appeal is worth your time

Here's a plain framework for deciding whether to file.

Step 1: Find your assessed value on the current notice. Do not use the estimated market value the assessor prints there. Use the actual assessed value, the number the tax is calculated from.

Step 2: Find your combined mill rate on the same notice or on your county assessor's website. Most publish it plainly.

Step 3: Estimate what your home would sell for today. Pull three to five recent sales of homes similar in size, age, and condition within a mile or two. County deed records and public listing sites give you this for free.

Step 4: Convert that estimated market value to assessed value using your jurisdiction's ratio. Most assessor sites publish it. If you can't find it, divide your current assessed value by last year's estimated market value on your notice to back into the ratio.

Step 5: Take the difference in assessed value and multiply by the mill rate divided by 1,000.

(Current Assessed Value minus Correct Assessed Value) x Mill Rate / 1,000 = Annual Overpayment

If the answer clears $200 to $300 a year and you have solid comparable-sale evidence, filing is almost certainly worth it. Filing is free in most counties. The only real cost is a few hours. If you trust your evidence but not the process, the TaxFightBack appeal kit hands you templates and step-by-step guidance so you're not staring at a blank page.

One honest caveat. Nobody has reliable national data comparing self-represented and represented success rates in property tax appeals. The closest published numbers come from the Illinois Property Tax Appeal Board, which reported that represented taxpayers won reductions in about 68% of appealed cases in recent years, while self-represented rates weren't tracked separately. ^[11] In most places the quality of your evidence matters more than who presents it, which is why gathering strong comparable sales is the main job.

Frequently asked questions

What is a mill rate in simple terms?

A mill rate is the tax you pay per $1,000 of assessed value. One mill equals $1 of tax per $1,000. A mill rate of 25 means you pay $25 for every $1,000 your property is assessed at. Multiply your assessed value by the mill rate and divide by 1,000 to get your annual property tax bill.

What is a good mill rate for property tax?

There's no universal "good" rate. What matters is the effective rate: total tax divided by actual market value. The Lincoln Institute's 2023 study found U.S. effective rates from about 0.28% in Hawaii to 2.47% in Illinois. A 10-mill nominal rate in a county that assesses at 100% of market value is heavier than a 40-mill rate in a county that assesses at 15%.

How often do mill rates change?

Most jurisdictions recompute mill rates every year during the annual budget process. If total assessed value in the district rises after a reassessment, the rate may drop to collect the same revenue. If the government wants more money, it may hold the rate flat or raise it. States with rollback or truth-in-taxation laws require public notice or a hearing before collecting more than last year's total revenue.

Is mill rate the same as property tax rate?

Yes, functionally. "Mill rate," "millage rate," and "property tax rate" all name the same variable: the factor applied to assessed value to produce a bill. The difference is presentation. Some states express it per $1,000 (mills), others per $100 (Texas), others as a decimal percentage. Convert to mills by multiplying a per-$100 rate by 10, or a decimal rate by 1,000.

What part of my property tax bill has the highest mill rate?

In most U.S. jurisdictions the school district levy is the largest single piece, often 50% to 70% of the combined mill rate. The county general fund is usually second. Special districts (fire, library, parks) contribute smaller shares. You can see the breakdown on your annual tax notice or on the county treasurer's website, which lists each taxing district's levy separately.

Can I lower my property taxes by challenging the mill rate?

Not directly as an individual. Mill rates are set through public legislative processes by elected boards and commissions. Your practical path to a lower bill is appealing your assessed value, which shrinks the base the mill rate hits. A successful assessment appeal cuts your bill across every taxing district's levy at once, since all of them use the same assessed value.

How does the mill rate affect my appeal savings?

The mill rate tells you exactly what each dollar of assessment reduction is worth. At a combined 30-mill rate, every $1,000 reduction saves $30 a year. On a $40,000 over-assessment (not unusual after a hot-market reassessment), that's $1,200 a year. In high-mill jurisdictions like New Jersey or the Illinois suburbs, the same dollar reduction saves even more.

Why do two houses on the same street pay different property taxes?

Different assessed values are the usual cause. One owner may have appealed successfully, filed an exemption the other hasn't, or bought at a different time (which matters in states like California, where Proposition 13 ties assessment to purchase price). Different mill rates can also apply if the parcels sit in different school or special districts, which sometimes split at odd boundaries mid-block.

How does California Proposition 13 interact with the mill rate?

Proposition 13 caps the base property tax rate at 1% of assessed value, roughly 10 mills. It also limits annual increases in assessed value to 2% until the property sells, when it resets to the sale price. So nearly all California homeowners pay the same nominal mill rate, but assessed values diverge sharply between longtime owners and recent buyers. The variance lives in the base, not the rate. ^[5]

What is a floating mill rate vs. a fixed mill rate?

A fixed mill rate stays at a voter-approved or legislatively set level no matter how assessed values move. A floating (or variable) rate adjusts each year so the jurisdiction collects its budgeted revenue even as values shift. Most school district and municipal levies float. Voter-approved bond measures and special levies are often fixed at a rate set when the bond was authorized, lasting until the debt is retired.

How do I find the mill rate for my specific address?

Your annual assessment notice lists the combined mill rate, and so does your county treasurer or tax collector's website. Search your county name plus "mill rate" or "tax rate table." Many counties publish a rate sheet by taxing district, which lets you verify each component. If you're inside a municipality, the city finance office or the county assessor usually posts rate archives going back several years.

Does a higher assessed value always mean a higher tax bill?

Almost always, yes. Higher assessed value times the same mill rate produces a higher bill. The exception is when you gain a new exemption large enough to offset the increase, or the county rolls back the mill rate enough to fully cancel the higher value. In practice, most homeowners in a rising-value market see higher bills unless they appeal or a meaningful new exemption kicks in.

What is an equalization rate and how does it relate to mill rate?

An equalization rate (used prominently in New York) measures how closely a municipality's assessed values track actual market values. A rate of 80% means the town assesses at 80% of full market value on average. The state applies this rate to equalize assessments across towns when apportioning school taxes. It doesn't change your individual mill rate, but it affects how school tax revenue is split between towns with different assessment practices.

Sources

1. Cook County Assessor's Office, Assessment Levels and Incentives: Cook County residential property is assessed at 10% of market value; commercial at 25%
2. Texas Comptroller of Public Accounts, Property Tax Basics: Texas expresses property tax rates per $100 of assessed value and mandates 100% market value assessment
3. Maricopa County Assessor's Office, Property Tax Overview: Maricopa County publishes combined mill rates with individual levies from county, cities, school districts, and community colleges
4. Lincoln Institute of Land Policy, 50-State Property Tax Comparison Study, 2023: Effective property tax rates across major U.S. cities ranged from approximately 0.28% in Hawaii to 2.47% in Illinois in 2023; national median near 1.0%
5. California State Board of Equalization, Proposition 13 Overview: Proposition 13 caps base property tax rate at 1% of assessed value and limits annual assessment increases to 2% until the property sells
6. Texas Comptroller of Public Accounts, Truth-in-Taxation: Texas Truth-in-Taxation law requires jurisdictions to publish a no-new-revenue rate and hold a public hearing before exceeding prior year revenue
7. Bexar Appraisal District, Protest and Appeal Procedures: Bexar County property owners file protests with the Appraisal Review Board
8. Georgia Department of Revenue, Property Tax Exemptions: Georgia offers a basic $2,000 state homestead exemption; counties stack additional local exemptions on top
9. Texas Comptroller of Public Accounts, Disabled Veteran and Surviving Spouse Exemptions: Texas provides a 100% homestead exemption for veterans rated 100% disabled
10. Minnesota Department of Revenue, Property Tax Class Rates: Minnesota applies class rates of 1.0% on the first $500,000 of homestead residential value, 1.5% on commercial/industrial, and 1.25% on apartment property
11. Illinois Property Tax Appeal Board, Annual Report: Represented taxpayers achieved reductions in about 68% of appealed cases in recent years; self-represented rates were not separately tracked