Equalized Assessed Value (EAV) in Illinois Explained: Formula, Examples & 2025 Multipliers
By Harsha N Hegde
Most Illinois homeowners see “EAV” on their property tax bills but don’t know what it means.
EAV—Equalized Assessed Value—is a standardized number the state uses to ensure fairness across counties.
This guide breaks down how EAV is calculated, why Illinois applies equalization, and how it affects your property tax bill.
TL;DR
EAV = Assessed Value × State Equalization Factor
Property Tax = (EAV − Exemptions) × Composite Tax RateIllinois sets one equalization factor per county per year; it does not vary by property type.
Farmland acreage/buildings and coal properties are excluded; farm homesites and residences are not.
What is EAV?
Illinois statutes define Equalized Assessed Value as an assessed value adjusted by the Illinois Department of Revenue (IDOR).
In practice, your local assessed value is multiplied by the county’s state equalization factor (also called the multiplier) to reach EAV.
Why equalization exists
Illinois law targets 33⅓% of market (fair cash) value as the average assessment level.
Because counties often fall above or below that benchmark, IDOR studies sales and issues a county-wide equalization factor each year to bring the county back to the 33⅓% target.
This keeps tax burdens uniform across the state.
County clerks then compute tax rates by dividing each taxing body’s levy by the district’s total EAV.
Exemptions reduce EAV before tax rates are applied.
Example: In Cook County, the Homeowner and Senior exemptions reduce EAV by $10,000 and $8,000 respectively.
If your local composite rate is 6%, each exemption saves about $600 and $480 respectively.
Intra-county vs. State Equalization
Before IDOR applies its statewide equalization factor, Cook County performs intra-county equalization—adjusting township assessments to align with countywide averages.
This ensures that townships like Northfield, Niles, and Schaumburg are internally consistent before the state adds its uniform factor.
Other counties such as DuPage and Lake typically do not apply separate township factors.
Cook County Equalization Factors (Last 5 Years)
| Year | Multiplier | % Change | Source |
|---|---|---|---|
| 2025 | 3.0355 | — | IDOR |
| 2024 | 2.9237 | +3.8% | IDOR |
| 2023 | 3.0027 | -2.6% | IDOR |
| 2022 | 3.0027 | — | IDOR |
| 2021 | 3.2234 | -6.9% | IDOR |
These multipliers show that Cook County assessments are, on average, about one-third of market value—IDOR raises them roughly 3× to meet the 33⅓% statutory target.
Township Equalization Factors (Selected Illinois Counties, 2024)
| County | Township | Factor | Notes |
|---|---|---|---|
| Cook | Northfield | 1.0000 | County-wide applied |
| DuPage | Milton | 1.0000 | No intra-county factor |
| Lake | Libertyville | 1.0000 | Uniform assessment |
| Kane | Dundee | 1.0250 | Slight upward adjustment |
Township equalization is local and temporary—it only affects assessments before the state equalization factor is applied.
Worked Example (Cook County)
Let’s compute a Cook County homeowner’s estimated 2025 property tax step-by-step.
Assessed value: $30,000
Equalization factor (2025): 3.0355
Exemptions: $18,000 (Homeowner + Senior)
Composite tax rate: 6%
EAV = 30,000 × 3.0355 = 91,065
Taxable EAV = 91,065 − 18,000 = 73,065
Property Tax = 73,065 × 6% = 4,384So the estimated tax bill is about $4,384.
Want to know how your township’s tax rate affects your bill?
See our Cook County Composite Tax Rates Guide.
Try It Yourself
Illinois EAV Calculator
Estimate Equalized Assessed Value (EAV), net EAV after exemptions, and an approximate tax using your composite tax rate.
What this calculator does
EAV = AV × state equalization factor.Net EAV = EAV − exemptions(floored at 0).Estimated tax = Net EAV × (composite rate ÷ 100).- Actual bills depend on final certified levies, rates, and your exact exemption amounts.
How Other States Handle Equalization
Illinois is one of few states that uses a statewide equalization factor.
- Indiana uses trending to adjust to market value—no state multiplier.
- Texas appraises directly at market value each year—no equalization.
- Michigan uses county-level equalization to align assessments with true cash value.
These differences show why Illinois homeowners should understand EAV—it’s the single number linking local assessments to actual tax bills.
How to find your county’s equalization factor
You can look up the latest equalization factor for your county at:
👉 Illinois Department of Revenue - Equalization Factors
FAQs
What is Equalized Assessed Value (EAV)?
It’s your property’s locally assessed value multiplied by the state’s equalization factor to make assessments uniform across counties.
Who decides the equalization factor?
The Illinois Department of Revenue reviews sales data and determines one factor per county each year.
Does EAV affect my property tax bill?
Yes. Taxing districts use total EAV to set tax rates. The higher your EAV (after exemptions), the higher your tax bill.
Why does Cook County’s equalization factor seem higher than others?
Because Cook County assessments typically average below 33⅓% of market value, the IDOR applies a higher multiplier (around 3.0) to bring them up to the statewide target.
About the Author
Harsha N Hegde is the founder of squaredeal.tax, a DIY platform that helps homeowners protest unfair property tax assessments. He has helped thousands of homeowners save money using comps-based evidence and practical guidance.
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