Free Illinois Income Tax Calculator 2026 — Flat 4.95% Rate

Illinois taxes income at a constitutionally mandated flat rate — no brackets, no standard deduction. Enter your income, filing status, and dependents and this calculator applies Illinois’s real 2026 figures — the 4.95% flat rate, the $2,925 personal exemption, and the senior/blind add-on — to estimate your tax, effective rate, and take-home pay. Educational estimate only; your numbers never leave the browser.

How it works

The calculator starts with gross income and subtracts pre-tax deductions (401(k), HSA) to get adjusted gross income. It then subtracts Illinois personal exemptions — $2,925 per filer and per dependent, plus $1,000 if 65+ or legally blind — unless AGI is over $250,000 ($500,000 joint), where Illinois disallows exemptions entirely. The remainder is taxed at Illinois’s flat 4.95% rate, the same rate that applies to every dollar of taxable income because the Illinois constitution mandates a flat income tax.

Everyday uses

• Illinois workers — estimate your state withholding and avoid an April surprise.
• New residents — see what a move to Chicago or Springfield costs in state tax.
• Retirees — confirm your pension, Social Security, and 401(k) distributions stay exempt from Illinois tax.
• Job changers — compare offers by real take-home, not headline salary.
• Freelancers — rough out quarterly Illinois estimated payments.