Illinois Paycheck Calculator
Use this calculator to estimate your net pay per pay period in Illinois, factoring in federal and state taxes, FICA contributions, and common deductions.
Understanding Your Illinois Paycheck
Calculating your net pay in Illinois involves several components, including federal income tax, FICA taxes (Social Security and Medicare), and Illinois state income tax, along with any pre-tax or post-tax deductions you may have. This calculator provides an estimate based on common tax laws and withholding methods.
1. Gross Pay
This is your total earnings before any taxes or deductions are taken out. It's the starting point for all paycheck calculations.
2. Federal Income Tax
Federal income tax is a progressive tax, meaning higher earners pay a larger percentage of their income in taxes. The amount withheld from your paycheck depends on your gross income, filing status (Single, Married Filing Jointly, Head of Household), and the number of allowances or adjustments you claim on your W-4 form. While modern W-4s don't use "allowances" directly, many calculators use a simplified allowance system to estimate the reduction in taxable income for withholding purposes.
The calculator uses a simplified approximation of the 2024 federal tax brackets and standard deductions to estimate your annual federal tax liability, which is then prorated per pay period.
3. FICA Taxes (Social Security and Medicare)
- Social Security: This tax funds retirement, disability, and survivor benefits. For 2024, the rate is 6.2% on earnings up to an annual wage base limit of $168,600.
- Medicare: This tax funds hospital insurance for the elderly and disabled. For 2024, the rate is 1.45% on all earnings, with no wage base limit.
These taxes are mandatory for most employees and are deducted directly from your gross pay.
4. Illinois State Income Tax
Illinois has a flat income tax rate. For 2024, the rate is 4.95% of your taxable income. You are allowed to claim exemptions for yourself and any dependents, which reduce your taxable income for state purposes. Each allowance claimed reduces your annual taxable income by a set amount (e.g., $2,550 for 2024).
5. Pre-Tax Deductions
These are deductions taken from your gross pay before taxes are calculated. Common examples include contributions to a 401(k) or traditional IRA, health insurance premiums, and Flexible Spending Account (FSA) contributions. Pre-tax deductions reduce your taxable income, thereby lowering your federal and state income tax liability.
6. Post-Tax Deductions
These deductions are taken from your pay after all taxes have been calculated and withheld. Examples include Roth 401(k) contributions, union dues, garnishments, or charitable contributions. Post-tax deductions do not reduce your taxable income.
7. Net Pay
Your net pay, or "take-home pay," is the amount you receive after all federal taxes, state taxes, FICA taxes, and all deductions (pre-tax and post-tax) have been subtracted from your gross pay.
Important Considerations
- Accuracy: This calculator provides an estimate. Actual withholding can vary based on specific employer payroll systems, additional withholding requests, and other factors.
- Tax Law Changes: Tax laws and rates can change annually. This calculator is based on 2024 tax information.
- Local Taxes: This calculator does not account for any potential local taxes, which are rare in Illinois but can exist in some municipalities.
- Other Income/Deductions: This calculator focuses on standard employment income. Other income sources or complex deductions (e.g., self-employment tax, itemized deductions) are not included.
For precise tax advice or detailed planning, it's always best to consult with a qualified tax professional.
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function calculatePaycheck() {
// Constants for 2024 (approximate for calculator simplicity)
var SS_RATE = 0.062;
var SS_WAGE_BASE = 168600; // Social Security wage base limit
var MEDICARE_RATE = 0.0145;
var IL_STATE_TAX_RATE = 0.0495;
var IL_EXEMPTION_PER_ALLOWANCE = 2550; // Annual Illinois exemption per allowance
var FEDERAL_ALLOWANCE_VALUE = 4700; // Simplified annual value per federal allowance for calculation
// Federal Standard Deductions (Annual 2024)
var FEDERAL_STANDARD_DEDUCTIONS = {
'single': 14600,
'married': 29200,
'hoh': 21900
};
// Federal Tax Brackets (Annual 2024)
var FEDERAL_TAX_BRACKETS = {
'single': [
{ rate: 0.10, cap: 11600 },
{ rate: 0.12, cap: 47150 },
{ rate: 0.22, cap: 100525 },
{ rate: 0.24, cap: 191950 },
{ rate: 0.32, cap: 243725 },
{ rate: 0.35, cap: 609350 },
{ rate: 0.37, cap: Infinity }
],
'married': [
{ rate: 0.10, cap: 23200 },
{ rate: 0.12, cap: 94300 },
{ rate: 0.22, cap: 201050 },
{ rate: 0.24, cap: 383900 },
{ rate: 0.32, cap: 487450 },
{ rate: 0.35, cap: 731200 },
{ rate: 0.37, cap: Infinity }
],
'hoh': [
{ rate: 0.10, cap: 16550 },
{ rate: 0.12, cap: 63100 },
{ rate: 0.22, cap: 100500 },
{ rate: 0.24, cap: 191950 },
{ rate: 0.32, cap: 243700 },
{ rate: 0.35, cap: 609350 },
{ rate: 0.37, cap: Infinity }
]
};
// Get input values
var grossPay = parseFloat(document.getElementById('grossPay').value);
var payFrequencyMultiplier = parseFloat(document.getElementById('payFrequency').value);
var federalFilingStatus = document.getElementById('federalFilingStatus').value;
var federalAllowances = parseInt(document.getElementById('federalAllowances').value);
var illinoisFilingStatus = document.getElementById('illinoisFilingStatus').value; // Not directly used in IL tax calc, but kept for consistency
var illinoisAllowances = parseInt(document.getElementById('illinoisAllowances').value);
var preTaxDeductions = parseFloat(document.getElementById('preTaxDeductions').value);
var postTaxDeductions = parseFloat(document.getElementById('postTaxDeductions').value);
// Validate inputs
if (isNaN(grossPay) || grossPay < 0 ||
isNaN(federalAllowances) || federalAllowances < 0 ||
isNaN(illinoisAllowances) || illinoisAllowances < 0 ||
isNaN(preTaxDeductions) || preTaxDeductions < 0 ||
isNaN(postTaxDeductions) || postTaxDeductions < 0) {
document.getElementById('result').innerHTML = 'Please enter valid positive numbers for all fields.';
return;
}
// Annualize amounts
var annualGrossPay = grossPay * payFrequencyMultiplier;
var annualPreTaxDeductions = preTaxDeductions * payFrequencyMultiplier;
var annualPostTaxDeductions = postTaxDeductions * payFrequencyMultiplier;
// 1. Calculate FICA Taxes (Annual)
var ssTaxable = Math.min(annualGrossPay, SS_WAGE_BASE);
var annualSSTax = ssTaxable * SS_RATE;
var annualMedicareTax = annualGrossPay * MEDICARE_RATE;
var annualFICATax = annualSSTax + annualMedicareTax;
// 2. Calculate Federal Income Tax (Annual)
var federalTaxableIncome = annualGrossPay – annualPreTaxDeductions;
var standardDeduction = FEDERAL_STANDARD_DEDUCTIONS[federalFilingStatus];
var allowanceDeduction = federalAllowances * FEDERAL_ALLOWANCE_VALUE;
// Reduce taxable income by standard deduction and allowances
federalTaxableIncome = Math.max(0, federalTaxableIncome – (standardDeduction + allowanceDeduction));
var annualFederalTax = 0;
var brackets = FEDERAL_TAX_BRACKETS[federalFilingStatus];
var previousCap = 0;
for (var i = 0; i previousCap) {
var taxableInBracket = Math.min(federalTaxableIncome, bracket.cap) – previousCap;
annualFederalTax += taxableInBracket * bracket.rate;
}
previousCap = bracket.cap;
if (federalTaxableIncome <= bracket.cap) {
break;
}
}
annualFederalTax = Math.max(0, annualFederalTax); // Ensure tax is not negative
// 3. Calculate Illinois State Income Tax (Annual)
var illinoisExemptions = illinoisAllowances * IL_EXEMPTION_PER_ALLOWANCE;
var illinoisTaxableIncome = Math.max(0, annualGrossPay – annualPreTaxDeductions – illinoisExemptions);
var annualIllinoisTax = illinoisTaxableIncome * IL_STATE_TAX_RATE;
// Calculate per-period amounts
var ficaTaxPerPeriod = annualFICATax / payFrequencyMultiplier;
var federalTaxPerPeriod = annualFederalTax / payFrequencyMultiplier;
var illinoisTaxPerPeriod = annualIllinoisTax / payFrequencyMultiplier;
// Calculate Net Pay per Period
var netPay = grossPay – preTaxDeductions – ficaTaxPerPeriod – federalTaxPerPeriod – illinoisTaxPerPeriod – postTaxDeductions;
// Format results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2,
maximumFractionDigits: 2
});
var resultHTML = '
Estimated Paycheck Breakdown
';
resultHTML += '
Gross Pay per Period: ' + formatter.format(grossPay) + ";
resultHTML += '
Pre-Tax Deductions: ' + formatter.format(preTaxDeductions) + ";
resultHTML += '
Federal Income Tax: ' + formatter.format(federalTaxPerPeriod) + ";
resultHTML += '
FICA Taxes (Social Security & Medicare): ' + formatter.format(ficaTaxPerPeriod) + ";
resultHTML += '
Illinois State Tax: ' + formatter.format(illinoisTaxPerPeriod) + ";
resultHTML += '
Post-Tax Deductions: ' + formatter.format(postTaxDeductions) + ";
resultHTML += '
Net Pay per Period: ' + formatter.format(netPay) + ";
document.getElementById('result').innerHTML = resultHTML;
}
// Calculate on page load with default values
document.addEventListener('DOMContentLoaded', calculatePaycheck);