Free IRS Withholding Calculator

Your employer withholds federal income tax from every paycheck based on your W-4 settings. Too little withholding means a surprise tax bill (and possibly penalties) in April. Too much means you've been giving the government an interest-free loan all year. This calculator finds the sweet spot using IRS Publication 15-T methodology and 2026 tax brackets.

Here's how federal withholding works: your employer takes your gross pay per paycheck, subtracts pre-tax deductions (401(k), HSA, commuter benefits), and multiplies by the number of pay periods to annualize your wages. Then they subtract the standard deduction ($15,000 single, $30,000 married, $22,500 head of household) and apply the progressive federal brackets (10%–37%). The result is divided by your pay periods to get the per-paycheck withholding amount.

FICA is separate from federal income tax withholding and is not affected by your W-4. Social Security takes 6.2% of wages up to $176,100, and Medicare takes 1.45% on all wages plus 0.9% additional Medicare above $200,000 (single) or $250,000 (married). Your total paycheck deduction is federal withholding + FICA + pre-tax deductions.

The modern W-4 (2020 and later) doesn't use allowances anymore. Instead: Step 1 is filing status, Step 2 handles multiple jobs, Step 3 claims dependents ($2,000 credit per child), and Step 4 lets you add extra withholding (4c) or report other income (4a) and deductions (4b). If you're under-withheld, add the extra amount to Step 4(c) — this calculator tells you exactly how much.

A real example: single filer, $75,000/year, bi-weekly pay. Federal withholding should be about $335 per paycheck. If you're currently having $250 withheld, you'd owe roughly $2,210 at tax time plus potential penalties. Add $85 to Step 4(c) of your W-4 and you're covered.