How it works
The calculator takes your gross pay for one pay period, subtracts the pre-tax deductions you entered, and works out each tax on its own line. Federal income tax follows the percentage method in IRS Publication 15-T (2026), Federal Income Tax Withholding Methods, using your W-4 entries. Social Security is 6.2% of wages up to $184,500 for the year (SSA; IRS Publication 15 (2026)). Medicare is 1.45% of all wages, plus Additional Medicare Tax of 0.9% on wages over $200,000 (IRS Publication 15 (2026)).
Illinois income tax follows the formula in Illinois Department of Revenue, Booklet IL-700-T, Illinois Withholding Tax Tables (2026). Each IL-W-4 basic allowance is worth $2,925 a year and each additional allowance $1,000. The calculator adds up your allowances, divides the total by the number of paychecks in the year, subtracts that from the paycheck's wages, and applies the flat rate of 4.95% to what is left. Illinois has one rate for every income level and every filing status, so your IL-W-4 allowances are the only state entries that change the amount.
Illinois has no employee-paid state disability or paid family leave deduction, and state unemployment insurance is paid by employers to the Illinois Department of Employment Security. Chicago and other Illinois cities and counties do not levy a local income tax on wages, so there is no local tax field on this page.
Not included: employer-paid taxes, after-tax deductions such as Roth 401(k) or union dues, garnishments, bonuses and other supplemental wages, tips, and any refund or balance due when you file. Your employer's payroll may round differently or use the IL-700-T tables instead of the formula.
Worked example
Take a $65,000 salary paid biweekly, filing single on the W-4, with one IL-W-4 basic allowance and no other deductions. Gross pay is $65,000 divided by 26 paychecks, which is $2,500.00. Federal withholding under Pub 15-T is $216.15, Social Security is $155.00 and Medicare is $36.25. For Illinois, the calculator divides the one allowance of $2,925 by 26, subtracts it from the paycheck, and applies 4.95%: Illinois withholding is $118.18. Take-home pay is $1,974.42 per paycheck, or $51,334.92 over the year.
Frequently asked questions
What is the Illinois income tax rate for 2026?
Illinois taxes wages at a flat 4.95% for every income level and filing status (Illinois Department of Revenue, IL-700-T (2026)).
How much is taken out of a paycheck in Illinois?
An Illinois paycheck has federal income tax, Social Security, Medicare and Illinois income tax withheld. The total depends on your pay, W-4 and IL-W-4; with the example above it comes to 21.0% of gross pay.
How do IL-W-4 allowances work?
The IL-W-4 worksheet sets the count: basic allowances on Line 1 for yourself, your spouse and dependents, and additional allowances on Line 2 for age 65 or older or legal blindness. Each basic allowance lowers the wages Illinois tax is figured on by $2,925 a year (Illinois Department of Revenue, IL-700-T (2026)).
Does Chicago have a city income tax?
No. Chicago does not withhold a city income tax from wages, so a Chicago paycheck has the same tax lines as one anywhere else in Illinois.
Do I pay Illinois tax if I live in Iowa, Kentucky, Michigan or Wisconsin?
Illinois has reciprocal agreements with these four states, so a resident of one of them who works in Illinois can file Form IL-W-5-NR and have tax withheld for the home state instead (Illinois Department of Revenue, 2026). This calculator applies Illinois withholding.
Is my 401(k) taxed by Illinois?
Traditional 401(k) contributions are left out of Illinois taxable wages, the same as for federal income tax, so a 401(k) setting lowers both lines. Social Security and Medicare still apply to them.