Estimate your W-2 employee tax withholding — federal income tax, Social Security, Medicare, and state tax — for 2026.
401(k) amounts reduce income-tax wages only. HSA and health FSA amounts are treated as pre-tax cafeteria-plan (Section 125) payroll deductions within the annual limits, so they also reduce Social Security and Medicare wages. After-tax HSA contributions and dependent-care FSAs are not modeled.
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Get in Touch →W-2 employees have federal income tax withheld each paycheck using the annualized percentage method in IRS Publication 15-T — your per-period gross is multiplied by pay periods to estimate annual income, taxes are calculated on that amount, then divided back to a per-period withholding amount.
Your actual withholding may differ based on W-4 Step 3 (child tax credits), Step 4a (additional income like rental or investments), Step 4b (itemized deductions above the standard deduction), or Step 4c (additional flat withholding). This calculator assumes a standard W-4 with no adjustments beyond filing status. As in IRS Publication 15-T, married filing separately is withheld on the single rate schedule. Employers also withhold the 0.9% Additional Medicare Tax on wages above $200,000 for every filing status. Your actual threshold ($250,000 married filing jointly, $125,000 married filing separately) is settled on your tax return.
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Get in Touch →W-2 Box 1 (federal wages) is your gross pay minus pre-tax deductions like traditional 401(k) contributions, FSA, and other Section 125 benefits. Social Security wages (Box 3) typically equal gross pay minus 401(k) but may be reduced by other Section 125 deductions like employer-sponsored HSA contributions.
Traditional 401(k) contributions reduce federal income tax withholding but NOT Social Security or Medicare — FICA applies to gross wages regardless. However, HSA contributions through a Section 125 cafeteria plan typically reduce both income tax and FICA. Roth 401(k) contributions reduce neither. This calculator treats the HSA / health FSA amount you enter as a cafeteria-plan deduction, so it reduces income tax, Social Security and Medicare.
Submit a new Form W-4 to your employer at any time. The IRS Tax Withholding Estimator at irs.gov/W4app can help you calculate the correct withholding to avoid owing at year-end or over-withholding unnecessarily.
Your employer sends you a W-2 each January reporting your prior-year wages and total federal, state, Social Security, and Medicare taxes withheld. You use these numbers to file your annual Form 1040 and reconcile whether you owe additional tax or are due a refund.
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