Illinois has one of the highest effective property tax burdens in the United States, and the way the bill is built is different from most states. Instead of taxing you directly on your home's market value, Illinois applies a statutory 33.33% assessment ratio to produce an Equalized Assessed Value (EAV), and only then layers the local county tax levy on top. This calculator walks through that exact two-step flow so you can estimate what you will actually owe each year.
Adjust the three sliders and every figure updates instantly. The result card shows your Equalized Assessed Value, the annual tax bill, the monthly equivalent, and the effective rate as a percentage of your home's market value — the number most buyers actually compare across states.
How to Use
- Enter the Home Market Value — the fair-market price the county assessor has placed on the property, or your purchase price if you just bought. If you do not know the assessed value, start with what you believe the home would sell for today.
- Confirm the Assessment Ratio. Illinois law sets residential property at 33.33% of fair-market value, so leave the default at 33.33% unless your county has notified you of a different fraction (commercial and vacant land are assessed at different ratios).
- Set the County Tax Rate (on EAV). This is the single biggest driver and the number people get wrong. In Chicago and most of Cook County the combined levy runs roughly 6–8% of EAV; downstate counties are often 2–5%. Use your last tax bill's "levy" or ask your county clerk for the current rate.
- Read the result card. The Annual Property Tax is what you owe for the year (usually split into two installments in Illinois). The Monthly Property Tax is what a lender will escrow into your mortgage payment. The Effective Rate tells you what the tax costs as a share of the home's market value — the cleanest number for comparing Illinois to California, Texas, Florida or Indiana.
If you are shopping for a home, the monthly figure is the one to add to your mortgage quote: a payment that looks affordable at the 6% rate can jump several hundred dollars once Cook County property tax is escrowed.
How Illinois Property Tax Is Actually Calculated
Illinois does not multiply your home's sale price directly by a tax rate. It uses a two-step equalization system laid out in the Illinois Property Tax Code:
Step 1 — EAV = Market Value × 33.33%
The county assessor estimates the property's fair-market value. State law then requires residential property to be assessed at one-third (33.33%) of that value. A home worth $400,000 is therefore assessed at roughly $133,320, regardless of what the tax rate ends up being.
Step 2 — Annual Tax = EAV × County Tax Rate
Local taxing bodies — the county, the city, the school district, the park district, the library, and any special bonds voted on by residents — each set their own levy. Those levies add up to a single combined rate applied to the EAV. In Chicago that combined rate is typically about 6.6% of EAV.
Worked example on a $400,000 Chicago home: EAV = $400,000 × 33.33% = $133,320. Annual tax = $133,320 × 6.6% = $8,799.12 per year, or about $733.26 per month. As a share of the $400,000 market value, that is an effective rate of about 2.20% — which is why Illinois routinely appears near the top of national effective-property-tax rankings.
The reason the math looks confusing is that the "6.6%" you see on a tax bill is a levy on EAV, not on market value. Multiplying 6.6% by the 33.33% assessment ratio gives you the roughly 2.2% effective rate that actually matters to your wallet.
Why Illinois Rates Vary So Much by County
The single most important fact about Illinois property tax is that it is not a state rate — it is a stack of locally voted levies. A home in Chicago carries the combined weight of Chicago Public Schools, the Cook County government, the City of Chicago, the Cook County Forest Preserve, and a long list of bonded indebtedness. A similar home in a rural downstate county has a far thinner layer of services, and the EAV levy drops to perhaps 2–4%.
That is why the same $400,000 house can cost you $8,800 a year in Cook County but only $3,000–$4,000 in a downstate county. Always plug in the actual county rate rather than a statewide average if you are comparing neighborhoods or counties.
Illinois also offers several exemptions that reduce the EAV before the levy is applied — the General Homestead Exemption (up to $10,000 in Cook County), the Senior Citizens Homestead Exemption, and the Disabled Persons Homestead Exemption. This calculator uses the raw EAV without exemptions; subtract your exemption amount from the EAV line and rerun the rate to see the after-exemption bill.
Examples
Example 1 — A typical Chicago home. A couple buys a $400,000 condo in Lincoln Park. The assessor pegs market value at $400,000, the statutory ratio is 33.33%, and the combined Cook County EAV levy is 6.6%. EAV is $133,320; annual tax is $8,799.12, or $733.26 per month escrowed into the mortgage. The effective rate on market value is 2.20%.
Example 2 — A million-dollar North Shore home. A family in Winnetka owns a home assessed at $1,500,000. With the same 33.33% ratio and a 6.6% EAV levy, EAV is $499,950 and the annual tax bill is about $32,996.70, or $2,749.72 per month. That is roughly 2.2% of market value — the reason North Shore towns consistently top the national "highest property taxes" lists.
Example 3 — A downstate home. A buyer in a central-Illinois town purchases a $200,000 bungalow. Market value $200,000 × 33.33% = $66,660 EAV. The local combined EAV levy is 3.5%, not 6.6%. Annual tax is $66,660 × 3.5% = $2,333.10, or about $194.43 per month. The effective rate on market value is 1.17% — half of Chicago's, which is why Illinois rates vary so widely from ZIP to ZIP.
FAQ
How is Illinois property tax calculated?
Illinois uses a two-step flow. First, the county assessor estimates the home's fair-market value. Residential property is then assessed at 33.33% of that value to produce the Equalized Assessed Value (EAV). Finally, your local combined tax rate — a stack of county, city, school and park levies — is multiplied by the EAV. Annual tax = (home value × 33.33%) × county EAV rate.
What is the average Illinois property tax rate?
The statewide average effective property tax rate (tax paid divided by home market value) is roughly 2.0–2.3%, which ranks Illinois among the highest-tax states in the country. Cook County and the collar counties typically run 2.1–2.5% effective, while many downstate counties are closer to 1.0–1.5%.
What is the property tax rate in Chicago?
Chicago's combined levy on Equalized Assessed Value is typically around 6–8%. Because EAV is only 33.33% of market value, that translates to an effective rate of roughly 2.0–2.5% of the home's market value. A $400,000 Chicago home usually carries an annual bill near $8,000–$9,000 before exemptions.
What is the 33.33% assessment ratio in Illinois?
Illinois state law requires residential property to be assessed at one-third (33.33%) of its fair-market value. This is why the number on your assessment notice looks like a third of the home's worth. Commercial, industrial and vacant land parcels are assessed at different statutory ratios.
How often are Illinois property taxes billed?
Most Illinois counties send two installments per year — usually due June 1 and September 1 (Cook County splits into two installments as well, with due dates that can shift year to year). Lenders typically collect one-twelfth of the estimated annual tax each month into an escrow account and pay the county on your behalf.
Do I get a homestead exemption?
Owner-occupied Illinois residences qualify for the General Homestead Exemption, which reduces the EAV by up to $10,000 in Cook County (and varying amounts elsewhere). Homeowners aged 65 or older may also claim the Senior Citizens Homestead Exemption. Apply through your county assessor; exemptions lower the EAV and therefore the final bill.
Are Illinois property taxes deductible?
On your federal return, state and local property taxes (SALT) are deductible up to a $10,000 annual cap ($5,000 if married filing separately). Illinois does not tax Social Security, but it does tax most retirement income at a flat 4.95% — so the trade-off between high property tax and other state taxes is worth modeling before you move.
Disclaimer
This Illinois property tax calculator is provided for informational purposes only and does not constitute financial, tax, or legal advice. Estimates are based on the inputs you enter and the statutory 33.33% assessment ratio; actual bills vary by county, by school district, by voted bonds, by your exemptions, and by the most recent equalization. Exemption amounts, due dates and levy rates change every year. Always confirm your exact obligation with your county treasurer or a qualified Illinois tax professional before making a purchase or refinancing decision.