Methodology and sources

Rules checked 12 November 2026 for tax year 2026. Calculations run in your browser; nothing you type is sent anywhere.

Federal income tax

We follow IRS Publication 15-T Worksheet 1A for Forms W-4 from 2020 or later. Taxable wages per check (after pre-tax 401(k) and Section 125 deductions) are annualized, Step 4(a) other income is added, Step 4(b) deductions and the worksheet's adjustment ($12,900 married filing jointly, $8,600 otherwise, or $0 if the Step 2 box is checked) are subtracted, and the result is run through the 2026 Annual Percentage Method table. Step 3 credits are spread across the year's checks and Step 4(c) extra withholding is added. Our results match the IRS wage-bracket tables in the same publication (tested to the dollar for single, married and head-of-household filers).

Social Security and Medicare

6.2% Social Security on wages up to $184,500 and 1.45% Medicare, plus 0.9% additional Medicare on wages above $200,000. Pre-tax 401(k) contributions don't reduce these; Section 125 health, HSA and FSA deductions do. For simplicity we average the Social Security cap and the 0.9% across the year; a real employer applies them on the check where you cross the threshold.

States

No wage tax: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Wyoming. Washington also has none, but we include its Paid Family & Medical Leave (1.13% × 71.43% employee share) and WA Cares (0.58%) premiums.
Illinois: 4.95% after $2,925 per Line 1 allowance and $1,000 per Line 2 allowance.
Michigan: 4.25% after $5,900 per exemption, plus an optional city rate.
North Carolina: 4.09% withholding rate after the NC standard deduction ($12,750, or $19,125 for head of household) and $2,500 per allowance, rounded to the dollar.
Pennsylvania: 3.07% of wages with no allowances; 401(k) deferrals are taxable for PA. Optional local Earned Income Tax rate.

Bonuses

Federal withholding at the 22% optional flat rate for supplemental wages (under $1 million), and each state's supplemental rate where it has one.

Not included

State unemployment or disability withholding in a few states (for example Alaska and Pennsylvania), PA's Local Services Tax, garnishments, and employer-specific rounding. Federal withholding is an estimate of tax prepaid, not your final tax bill. This site gives estimates only and isn't tax advice.