Tax Withholding Calculator
Calculate the tax withheld from a single paycheck given gross pay and a withholding rate. Use it to estimate what a flat withholding rate produces — for example, a state's flat income-tax rate or the bonus-flat-rate (22% supplemental wage withholding) used by US employers on certain payments.
Last updated: May 2026
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About this calculator
The formula is: withholding = gross pay × withholding rate ÷ 100. This is a flat-rate calculation, where a single percentage applies to the entire gross amount. It accurately models several real withholding scenarios: state income tax in flat-rate states (Illinois 4.95%, Massachusetts 5%, Colorado 4.4%), the US federal supplemental wage rate of 22% applied to bonuses and certain other payments, and FICA (Social Security at 6.2% + Medicare 1.45% = 7.65% combined) which is essentially flat across most income levels. It does NOT correctly model regular federal income tax withholding from a normal paycheck, which uses the IRS withholding tables and depends on filing status, dependents, multiple jobs, and other W-4 inputs — those produce an effective average rate that varies non-linearly with income. Edge cases: zero rate returns zero withholding; very high rates (above 50%) are unusual but valid mathematically (some bonus stacking can push effective rates above 40% combining federal + state + FICA). The result is the amount removed from a single paycheck; for annual withholding across multiple paychecks, multiply by the number of pay periods per year (52 weekly, 26 biweekly, 24 semimonthly, 12 monthly). Important: withholding is just a prepayment of your annual tax liability — what you actually owe is determined when you file your annual return. Over-withholding means a refund; under-withholding means a tax bill (and possibly an underpayment penalty if you owe more than $1,000 and didn't meet safe-harbor thresholds).
How to use
Example 1 — Bonus payment, federal supplemental rate. Your employer pays you a $5,000 year-end bonus and applies the standard 22% federal supplemental wage withholding. Enter 5000 for Gross Pay and 22 for Withholding Rate. Result: $1,100 federal income tax withheld. Verify: 5000 × 22 / 100 = $1,100. ✓ This is in addition to FICA (7.65%) and any state withholding. The 22% rate may over- or under-withhold relative to your actual marginal rate — high earners (32%+ bracket) typically owe more at tax time; lower earners (10–12% bracket) typically get refunds. Example 2 — Illinois state tax on a regular paycheck. Biweekly gross pay $2,400 in Illinois, which has a flat 4.95% state income tax. Enter 2400 and 4.95. Result: $118.80. Verify: 2400 × 4.95 / 100 = $118.80. ✓ Over 26 pay periods this totals $3,088.80 of state tax annually — close to the actual figure since Illinois's flat rate produces predictable withholding regardless of total income (subject only to small adjustments for allowances and exemptions).
Frequently asked questions
Does this calculator handle federal income tax withholding from a regular paycheck?
No — federal income tax withholding from regular wages uses the IRS withholding tables (Publication 15-T), which depend on filing status, number of pay periods per year, dependents from the W-4, multiple jobs adjustments, and other inputs. The actual algorithm is not a flat rate but a piecewise computation that approximates progressive bracket-based annual tax. This calculator applies a single flat rate and is correct only for flat-rate withholding scenarios: state flat-rate taxes, the 22% federal supplemental wage rate (used for bonuses and other non-regular payments), or FICA at 7.65%. For accurate paycheck withholding, use the IRS Tax Withholding Estimator (irs.gov/withholding) or a paycheck-specific calculator that applies the IRS tables.
What is the federal supplemental wage rate?
22% — the flat rate the IRS allows employers to apply to "supplemental wages" like bonuses, commissions, severance, and back pay. This rate is independent of the employee's W-4 settings; the employer just multiplies the supplemental payment by 22% (or 37% for amounts above $1 million in a single year) and remits that to the IRS as federal income tax withholding. The 22% rate may significantly over- or under-withhold relative to the employee's actual marginal rate. For a high earner already in the 32% bracket, a $50,000 bonus with 22% supplemental withholding under-collects federal tax by about $5,000, producing a tax bill at filing. For a low earner in the 12% bracket, the same withholding over-collects and produces a refund. This is a common cause of surprise tax outcomes; high earners receiving large bonuses should consider extra W-4 withholding throughout the year to avoid an April surprise.
What is the relationship between withholding and tax owed?
Withholding is a prepayment toward your eventual annual tax liability, not the tax itself. Throughout the year, federal income tax withholding accumulates from each paycheck and the IRS receives the funds; at year-end you file Form 1040 and compute your actual tax owed based on total income, deductions, and credits. If withholding exceeded the actual liability, you get a refund. If withholding fell short, you owe the difference and possibly an underpayment penalty (if you owed more than $1,000 and didn't meet safe-harbor thresholds of paying at least 100% of prior-year tax or 90% of current-year tax). The goal of withholding management is to roughly match — neither a large refund (an interest-free loan to the government) nor a large tax bill. The IRS Tax Withholding Estimator helps tune W-4 settings to land near zero balance.
What are the most common mistakes people make with withholding?
The biggest is using outdated W-4 information after major life events — getting married, divorced, having a child, or starting a second job all materially change tax liability, and forgetting to update the W-4 produces either large refunds or surprise tax bills. The second is over-withholding deliberately to "force savings" through the annual refund; that's an interest-free loan to the government rather than effective savings. The third is under-withholding from a second job because each employer only knows about their own portion of total income, missing the higher combined marginal rate. The fourth is forgetting that side-gig and self-employment income require quarterly estimated payments; W-2 withholding won't cover non-W-2 income. The fifth is forgetting state withholding; many states require separate state W-4 forms (or use the federal W-4) and they're easy to overlook. Finally, people are often surprised by the size of their federal vs. all-in deductions; FICA + federal + state + local + Medicare + insurance + 401(k) can take 30–40% of gross before take-home.
When should I not use this calculator?
Skip it for regular paycheck federal income tax withholding — that uses the IRS Publication 15-T tables, not a flat rate, and this calculator will mislead you. Use a dedicated paycheck calculator or the IRS Tax Withholding Estimator instead. It is the wrong tool for progressive-bracket state income tax (California, New York, federal-style states) — for those, use a state-specific calculator. Do not use it for self-employment tax (15.3% on net earnings up to the SS wage base, with the 92.35% adjustment) — use a dedicated SE tax calculator. It also doesn't handle the cap on Social Security wages ($168,600 in 2024, above which the 6.2% portion stops applying), variable Medicare rates (1.45% base + 0.9% additional above $200K/$250K thresholds), or any of the W-4 adjustment fields that real payroll systems use. For real money decisions, use a full paycheck or tax-software tool, not this simplified shortcut.