The Six Terms at a Glance
- Set by
- Your town, village or city assessor
- You see it
- Notice of changed assessment; tax bill
- Set by
- The market; the law tells the assessor to measure it from sales
- You see it
- Not printed anywhere for your home: it's what sales and appraisals show
- Set by
- Wisconsin Department of Revenue, certified August 15
- You see it
- DOR's reports, not your bill
- Set by
- DOR, every year, for every municipality
- You see it
- Bill ("Ave. Assmt. Ratio"); notice ("General Level of Assessment")
- Set by
- Arithmetic on the bill, required by state law
- You see it
- Tax bill
- Set by
- Each taxing body's levy, divided by assessed value
- You see it
- Tax bill ("Net Assessed Value Rate")
Summarized from the definitions below, each cited where it's explained.
Assessed Value
The dollar amount your assessor puts on your property for taxation, estimated as of January 1 and used for the taxes levied that December. It's the number the levy is applied to directly, and it decides your share of your own municipality's tax.(DOR Guide for Property Owners)
Wis. Stat. 70.32(1) sets the standard: the assessor values real property the way the Wisconsin Property Assessment Manual says, "at the full value which could ordinarily be obtained therefor at private sale," and has to consider recent arm's-length sales of the property itself, recent arm's-length sales of comparable property, and everything else that affects value under accepted appraisal practice. DOR's Assessment Manual quotes that section in full as the basis of every valuation (p. 9-8).
The law doesn't require 100% every year. Each municipality must assess at full value at least once every five years, which DOR reads as every major class of property within 10% of full value in the same year.(Wis. Stat. 70.05(5))(DOR guide) In between, assessing at a percentage of full value is fine as long as it's applied to everyone alike.(DOR form PR-301) Farmland is the exception: agricultural land is assessed on its use value, and undeveloped and agricultural forest land at 50% of full value, so none of the ratio math here applies to it.(WPAM p. 1-19)
Fair Market Value
DOR uses fair market value, full value and market value as one idea: the amount the property would sell for in an arm's-length sale on the open market, between a willing seller and a willing buyer, neither obliged to act. Its glossary takes that wording from a 1994 Wisconsin Supreme Court case, Waste Management v. Kenosha County Board of Review.(DOR guide, glossary) The Assessment Manual's short version is "the most probable price paid by a willing buyer to a willing seller in an arm's-length transaction" (p. 9-8), and it calls a property's own recent sale price the best indicator of it (p. 10-1).(WPAM)
Equalized Value
Every year, Wis. Stat. 70.57 has the Department of Revenue value all the taxable property in every county and municipality, by class, before August 15, from every source it has; the figure it sets down is "the full value according to its best judgment." That's the equalized value. DOR's guide describes it the same way: all taxable property in a municipality as of January 1, at market value, certified August 15, with agricultural land at use value and agricultural forest and undeveloped land at 50%.(DOR guide)
It exists because municipalities assess at different percentages of market value. To split a county or school levy fairly between them, the state needs every municipality on the same footing, 100% of full value. In DOR's words, assessed value keeps owners fair with each other inside a municipality, and equalized value keeps municipalities and counties fair with each other.(DOR guide) DOR sets it independently of the local roll: the assessor values each parcel, DOR values the whole town, village or city.(WPAM p. 1-19) So equalized value is never a value for your house; courts have said so too.(Wis. Stat. 70.32, annotations) For scale, Dane County's equalized value for 2025 was $117,343,578,900.(DOR)
Assessment Level and Assessment Ratio
DOR's glossary separates two words people use loosely. The assessment level is a municipality's total assessed value divided by its equalized value: assessed at $2,700,000 against an equalized $3,000,000 is a 90% level. The assessment ratio is the same division for one parcel, its assessment over its market value: assessed at $140,000, sold for $150,000, is a 93% ratio.(DOR guide, glossary) State law has DOR work out the level for every municipality, and each major class, every year.(Wis. Stat. 70.05(5)(c)) Bills and notices print the level under other names: "average assessment ratio" on the tax bill, "general level of assessment" on the notice.(PR-301)
Madison for 2025: the city's assessors valued its taxable property at $48,905,845,200, DOR at $50,194,154,700, a 97.43% level.(DOR Major Class Comparison) That's the average assessment ratio printed on every Madison bill for 2025.(City of Madison)
Estimated Fair Market Value
The one market-value figure on your bill. Wis. Stat. 74.09 defines it as your assessed value divided by the assessment ratio of all taxable property in your municipality, and requires it on the bill. DOR adds the point people miss: taxes are levied on the assessed value, not on the estimate. Farmland on use value gets no estimate.(DOR guide) Because it's one municipality-wide ratio applied to every home, your estimate can differ from what your home would really sell for, and Madison's assessor says to expect that.(City of Madison)
Mill Rate
A tax rate is the levy divided by the total assessed value, written in dollars per $1,000 of assessed value (mills). The "net assessed value rate" on your bill is every taxing body's mill rate added up, less the state's school levy credit, and it's the same as dollars per $1,000. DOR's own example: a $1,000,000 levy over $25,000,000 of assessed value is .04, $40 per $1,000, so a home assessed at $45,000 owes $1,800 before credits.(DOR guide)
A Bill, Worked Through
Source for this section: Dane County Treasurer, sample 2025 tax bill (City of Anytown)
The Dane County Treasurer publishes a sample 2025 bill for a made-up "City of Anytown" on the state's bill form. We use it because it's real county output with no real owner on it. The PDF cuts off the last digits of some boxes, so we show those exactly as printed (for example "395,2…") and work the exact math on the boxes that print in full.
- Assessed value. Land $81,500, improvements $313,7…, total $395,2…. This is what the tax is figured on.
- Average assessment ratio: 0.9858. Anytown assesses at about 98.6% of market value overall. (Anytown is fictional, so this isn't any real town's level; yours is on your bill.)
- Estimated fair market value. Assessed value divided by the ratio. On the land line: $81,500 ÷ 0.9858 = $82,674, which the bill prints rounded as $82,700. On the total: $395,2… ÷ 0.9858 comes to between $400,893 and $400,993, and the bill prints "400,9…".
- Net assessed value rate: 0.01787. That's $17.87 per $1,000 of assessed value, or 17.87 mills, after the school levy tax credit, which the bill says cut this owner's school taxes by $668.
- Tax before the two small credits. $395,2… × 0.01787 comes to $7,062–$7,064; the bill's jurisdiction lines (county, city, school district, technical college) add up to $7,065. The gap is rounding in the printed rate.
- Net property tax. Minus the First Dollar Credit ($91) and the Lottery and Gaming Credit ($274): $6,699.87, the amount due.
Notice what the estimated fair market value doesn't do: it never enters the tax. Change the ratio and the estimate moves, but the $6,699.87 doesn't. Every box on the bill is explained in your tax bill, line by line.
Assessed Value and Market Value Converter
Go from an assessment to the market value it implies, or from a market value to the assessment you'd expect at your municipality's level. Pick a Dane County municipality for its 2025 level from the state, or type the ratio printed on your own bill or notice (it's the better number when you have it).(DOR Major Class Comparison)
Levels: DOR's Final Major Class Comparison for 2025, all property (February 2026).(DOR) The mill rate is the "net assessed value rate" on your bill; it already includes the school levy credit, not the lottery or first dollar credits. An estimate for understanding your bill, not an appraisal.
What the Ratio Tells You
The level is how far your municipality's assessments sit from market value. It says nothing bad about your own assessment by itself: if everyone is at 80%, everyone pays their fair share at 80%. DOR notes that a level well above or below 100% can mean a community-wide revaluation is coming.(DOR guide) In 2025, 33 of Dane County's 60 municipalities were more than 10% off market value overall.(DOR) Who assesses each one and when it last revalued is on the Dane County assessors page.
What matters for you is your own ratio against that level. DOR's guide for owners puts it plainly: divide your assessed value by your home's current market value; if the result is similar to your municipality's level, your assessment is equitable. The Assessment Manual tells the Board of Review the same: once market value is proved, a ratio well above the municipality's level is conclusive proof the assessment should come down (p. 20-22).(WPAM) Turned around, the assessment you'd expect is your market value times the level, which is what the converter's second mode does.
This is how our free assessment check works: it compares your assessment with recent sales of similar homes at your municipality's level, not at 100%. What a new notice means and how fast its deadlines come is on your assessment notice, line by line.
Why "My Assessment Is Above Zillow" Isn't an Argument
It's the most common reason people think they're over-assessed, and it fails on two counts before anyone looks at the number.
It's the wrong comparison. Unless your municipality assesses at 100%, your assessment isn't supposed to equal market value. In the Town of Vermont, at a 59.40% level for 2025, a home that would sell for $400,000 is correctly assessed at about $237,600.(DOR) Comparing that with any market figure tells you nothing; comparing your ratio with the level does.(DOR guide)
It isn't evidence of value. Wis. Stat. 70.32(1) measures value from sales: recent arm's-length sales of your property and of reasonably comparable property. The evidence DOR names follows from that: your own recent purchase price first, then sales of comparable homes, and a professional appraisal as a reliable estimate.(DOR guide) The Assessment Manual has assessors watch asking and listing prices only as signs of where the market is heading, and treats the state's real estate transfer returns as the main source of sales data.(WPAM p. 9-21) At the Board of Review, the assessor's value is presumed correct until you show otherwise.(Wis. Stat. 70.47(8)(i)) An estimate from a website is none of those. If it rests on sales, find the sales and bring them.
The same goes for a neighbor's lower assessment: DOR calls comparing assessments a mistake, and says a reduction takes proof your property is over-assessed compared with sales.(DOR guide)
Mill Rates and Full Value Rates
A mill rate is set on assessed value, so it moves opposite to assessments. DOR's example: a $200,000 levy over $4,000,000 of assessed value is .05; if a revaluation doubles assessed value to $8,000,000 and the levy stays put, the rate halves to .025.(DOR guide) That's why a big jump in your assessment in a revaluation year doesn't mean your tax jumps by the same share.
It's also why assessed mill rates can't be compared between towns. In 2025, net rates outside Madison ran from 10.77 mills in the Town of Blue Mounds to 27.74 mills in the Village of Brooklyn.(Dane County Treasurer) But Blue Mounds assessed at 109.76% of market value and Brooklyn at 59.63%.(DOR)(DOR, Green County) Multiply each rate by its level and the gap shrinks: about 11.8 mills on market value in Blue Mounds and 16.5 in Brooklyn. DOR does this for whole districts with the full value rate, tax divided by equalized value, which it calls the rate to use for comparing districts. The 2025 effective full value rate was .01641 in Dane County ($16.41 per $1,000 of market value) and .01338 statewide.(DOR) To do it with your own bill, multiply the net assessed value rate by the ratio: Anytown's 17.87 mills × 0.9858 is about 17.6 mills on market value.
Every Dane County town and school district's rate, on the same house, is in property tax rates by town, and every county's in Wisconsin tax rates by county. How the levy becomes your bill is on the Wisconsin property tax guide.
Questions
Is Assessed Value the Same as Market Value?
Only where a municipality assesses at 100%. The law sets market value as the standard, but it lets each municipality drift between revaluations as long as it gets within 10% of full value at least once every five years. In 2025, Dane County's municipalities ranged from 59.40% to 109.76% of market value.
Why Is My Assessment Lower Than What My House Would Sell For?
Usually because your municipality's assessments haven't caught up with sale prices since its last revaluation. Everyone in it is behind by about the same share, so your part of the tax is still fair. Check the average assessment ratio on your bill: divide your assessment by it and you get the market value your assessment implies.
What Is Equalized Value Used For?
Splitting the county, school district and technical college levies among the municipalities they cover, and handing out state property tax relief. It's set for a whole municipality, never for one house.
What Is a Mill?
One dollar of tax per $1,000 of assessed value. A net assessed value rate of 0.01787 on a bill is 17.87 mills, or $17.87 per $1,000.
Does a Higher Assessment Mean a Higher Tax?
Not by itself. Your tax depends on your share of your municipality's total assessed value and on the levies. If every assessment doubles in a revaluation and the levy stays the same, the rate is cut in half and the average bill doesn't move.
Where Do I Find My Municipality's Assessment Ratio?
On your tax bill, as the average assessment ratio, and on an assessment notice as the general level of assessment (preliminary in spring). For Dane County, the converter on this page has every municipality's level for 2025.