Paycheck Tax Calculator

What This Calculator Does

The Paycheck Tax Calculator runs the IRS Publication 15-T (2025) percentage method — the exact math your employer's payroll system runs every pay period — and returns the federal income tax withheld from one paycheck. Plus Social Security, Medicare, the 0.9% additional Medicare surtax if you trigger it, and an optional state tax.

Withholding ≠ Tax Owed (And Why It Matters)

This is the most-confused concept in US payroll, and it's worth getting straight before you read your stub.

Tax owed is your actual federal income tax liability for the year. It's computed at filing time from your annual income, deductions, credits, and bracket math, and it lands on Line 24 of Form 1040.

Withholding is your employer's per-paycheck advance payment of your estimated annual tax. It's computed using the IRS-published Pub 15-T tables and your W-4 selections. Your employer doesn't know your full tax picture (other income, deductions, credits beyond what's on your W-4) — they're working with a simplified projection.

April 15 is when the two numbers reconcile. If you over-withheld during the year, the IRS refunds the difference. If you under-withheld, you owe the difference (plus possibly an underpayment penalty if the shortfall is large).

This calculator computes WITHHOLDING. For TAX OWED, see the Take-Home Pay Calculator or the Tax Bracket Calculator.

The Pub 15-T Percentage Method (Worksheet 1A)

The IRS publishes Publication 15-T every year — the Employer's Federal Income Tax Withholding Methods. It's the rulebook for payroll departments. The percentage method (Worksheet 1A) is the version most computerized payroll systems use; the alternative is the wage bracket method (Worksheet 1B), which produces slightly different (dollar-rounded) results from a lookup table.

The percentage method is straightforward in five steps:

1. Annualize the wage. Multiply this paycheck's gross by the number of pay periods in a year (52 for weekly, 26 for bi-weekly, 24 for semi-monthly, 12 for monthly).
2. Apply the standard withholding table. The table has 8 brackets (0%, 10%, 12%, 22%, 24%, 32%, 35%, 37%), each with a published threshold, base tax, and marginal rate. Pick the bracket your annualized wage falls into, take the base, add the marginal rate times the excess over the threshold. The result is your tentative annual tax.
3. Subtract the dependents credit (W-4 Step 3). $2,000 per qualifying child under 17, $500 per other dependent. This is an annual amount.
4. Divide back to the period. Take whatever's left and divide by the pay periods. That's your federal withholding for one paycheck.
5. Add extra withholding (W-4 Step 4c). If you elected any per-paycheck extra, it gets added on top.

That's it. Three of the four W-4 boxes are inputs to this math. The fourth — Step 2(c) checkbox for two-earner households — switches to a different table (effectively half-bracket); not modeled in v1 of this calculator.

The 2025 Pub 15-T Brackets (Standard Withholding)

For reference, here are the published brackets in this calculator (Worksheet 1A, Step 2 NOT checked). All amounts are annualized:

Single or Married Filing Separately

• $0 – $6,400: 0%
• $6,400 – $18,325: $0 + 10% of excess
• $18,325 – $54,875: $1,192.50 + 12%
• $54,875 – $109,750: $5,578.50 + 22%
• $109,750 – $203,700: $17,651 + 24%
• $203,700 – $256,925: $40,199 + 32%
• $256,925 – $632,750: $57,231 + 35%
• $632,750+: $188,769.75 + 37%

Married Filing Jointly

• $0 – $17,100: 0%
• $17,100 – $40,950: $0 + 10%
• $40,950 – $114,050: $2,385 + 12%
• $114,050 – $223,800: $11,157 + 22%
• $223,800 – $411,700: $35,302 + 24%
• $411,700 – $518,150: $80,398 + 32%
• $518,150 – $768,700: $114,462 + 35%
• $768,700+: $202,154.50 + 37%

Head of Household

• $0 – $13,900: 0%
• $13,900 – $30,900: $0 + 10%
• $30,900 – $78,750: $1,700 + 12%
• $78,750 – $117,250: $7,442 + 22%
• $117,250 – $211,200: $15,912 + 24%
• $211,200 – $264,400: $38,460 + 32%
• $264,400 – $640,250: $55,484 + 35%
• $640,250+: $187,031.50 + 37%

FICA — The Other Half of Your Paycheck Tax

Federal income tax is the big variable, but FICA (Social Security + Medicare) is the steady drumbeat. Every paycheck takes a flat 7.65% off the top:

Social Security: 6.2% of gross wages, but only up to the wage base ($176,100 in 2025). After your year-to-date wages cross that threshold, SS stops being withheld for the rest of the year. Your employer pays a matching 6.2% on top — self-employed pay both halves (12.4%).

Medicare: 1.45% of gross wages, no cap. On top, the 0.9% Additional Medicare Tax kicks in once year-to-date wages cross $200,000 (regardless of filing status — that's a per-employee threshold the employer enforces, separate from the higher $250k MFJ threshold that applies at filing).

FICA contributions don't depend on your W-4. Your employer withholds it on every dollar of wages (up to the SS cap), independent of dependents, filing status, or extra withholding.

State Income Tax

Modeled here as a single flat-rate input — the right level of detail for "what's roughly going to land in my bank account." Real state withholding tables look like Pub 15-T but at 50× the variety (each state plus DC has its own). Most states also have an analog to the W-4 (often called a "state W-4" or DE-4 in California, IT-2104 in New York, etc.) that drives state-specific withholding. For the nine no-tax states (Texas, Florida, Nevada, Tennessee, Washington, Wyoming, South Dakota, Alaska, New Hampshire), enter 0. For the rest, your effective rate from last year's return is the right input — total state tax owed divided by taxable income.

Annualizing vs Year-to-Date — A Subtle Distinction

The percentage method works by annualizing one paycheck to project your annual tax, then dividing back. This is correct ON AVERAGE across the year for a steady-paycheck worker, but it differs from a true year-to-date calculation in two situations:

Mid-year SS cap crossover. If your annualized wages exceed $176,100, the percentage method (as this calculator runs it) applies an averaged SS cap per check. The real payroll system tracks YTD and stops withholding SS the exact pay period you cross $176,100, then resumes nothing for the rest of the year. The annual total is the same; the per-check distribution shifts.

Variable-hour weeks. A week where you worked 60 hours instead of 40 gets annualized to 60×52, pushing you into higher brackets temporarily. Over the year, the IRS reconciles — you get a refund for the over-withholding on the heavy weeks. Real payroll systems handle this the same way.

Bottom line: this calculator is right on the IRS-published math for one paycheck. The pennies might differ slightly from your actual stub if your payroll system uses YTD-aware logic for SS or pre-tax deductions, but the federal income tax line should match.

How to Use This in Real Life

Auditing your withholding. Compare what this calculator says to your actual stub's "Federal Income Tax" line. If they're different by more than a few dollars and you don't have a pre-tax deduction explaining it (401k, health), call HR. Their payroll system might be running an old W-4 or applying a Step 2 checkbox you didn't tick.

Tuning your W-4. If you consistently get a big refund (over-withholding), claim more dependents on Step 3 — each $2,000 reduces annual withholding by $2,000 (paid out as $77 per bi-weekly check instead). If you consistently owe, the opposite: lower Step 3, or add extra withholding on Step 4(c).

Pre-paycheck estimating. Just started a new job? Know what's hitting your bank before HR cuts the first check. Plug in your gross, your W-4 plan, and your state rate. The net is what you'll see.

Comparing job offers across states. A $90k offer in Texas pays more per paycheck than a $90k offer in California — by 4-10% of gross, depending on the CA bracket you land in. Run both through this calculator with the state rate set appropriately.

What's NOT Modeled

Pre-tax 401(k) and Section 125 health insurance. These reduce your federal taxable wages (and FICA for Section 125) before the table runs. Use the Take-Home Pay Calculator, which models them.

W-4 Step 2(c) checkbox. Two-earner households should check this if both spouses work. It switches the IRS table to a half-bracket version designed for combined-income forecasting. Bigger withholding per check. Will model in v2.

W-4 Step 4(a) — other income. If you tell your employer to withhold for side income (1099, investment, rental), it goes on Step 4(a). Not modeled.

W-4 Step 4(b) — deductions beyond standard. Mortgage interest, charitable, etc. Not modeled.

State withholding tables. Modeled as a single flat rate, not state-specific.

Local/city tax. NYC, Philadelphia, San Francisco, Cleveland, and others add their own. Not modeled.

SDI / SUI. California SDI is 1.1% up to $153k. New York has its own SDI rules. Not modeled.

Garnishments, post-tax deductions, Roth 401(k), HSA, FSA. Lower your take-home but don't lower federal withholding (some lower FICA — HSA does, Roth does not). Not modeled.

The Big Software Version of This Calculation

ADP, Gusto, Paychex, QuickBooks Payroll, Rippling — they all run essentially this Pub 15-T calculation behind the scenes. The math is published. The complexity in their products is integration with year-to-date tracking, pre-tax deductions, state tax tables, local taxes, garnishments, and the W-2 generation at year-end. For a "what should my paycheck look like" question, you don't need any of that. Just the math.

Educational Tool, Not Tax Advice

This calculator implements the standard IRS Pub 15-T (2025) percentage method. It is not tax advice. For complex situations — equity comp, multiple jobs, business income, state-specific multi-state work — a CPA pays for themselves. For the exact number on your actual stub, your employer's payroll system is the source of truth; ask HR to walk you through any line that doesn't match.

Related Tools

For annual gross-to-net with pre-tax deductions and tax filing brackets, use the Take-Home Pay Calculator. For federal income tax bracket math without FICA, see the Tax Bracket Calculator. To convert between hourly and annual pay rates, use the Annual Income Calculator or Salary to Hourly.