How Our Calculators Work
Every number on this site is produced by a documented formula applied to a documented data table. This page explains the general approach; each calculator page lists its exact inputs, tables, and worked examples.
Data sources
- Federal income tax: IRS Revenue Procedure 2025-32 (tax year 2026), including the standard deduction and marginal brackets for Single and Married Filing Jointly. The "One Big Beautiful Bill" (P.L. 119-21) made the TCJA rate structure permanent and added an enhanced standard deduction through 2028.
- Payroll tax (FICA): Social Security Administration announcements — for 2026, a 6.2% Social Security tax up to the $184,500 wage base, 1.45% Medicare tax on all wages, plus 0.9% Additional Medicare Tax above $200,000 (single) / $250,000 (joint).
- State income tax: where a calculator includes state tax, the page names the state's 2026 tables or states explicitly that the state is not yet covered.
How we calculate
- Start from gross pay as you enter it (annual salary or hourly wage × hours).
- Subtract pre-tax deductions you specify (401(k), HSA, health premiums) to get an adjusted figure where applicable.
- Apply the standard deduction for your filing status to get federal taxable income. (We use the standard deduction, not itemized — most filers take the standard deduction.)
- Apply marginal brackets — only the income inside each bracket is taxed at that bracket's rate. Moving into a higher bracket never taxes all your income at the higher rate.
- Apply FICA to the appropriate wage base.
- Divide by pay frequency for per-paycheck figures.
Verification process
- Every January we re-check federal tables against IRS publications before updating the site's tax year.
- Each calculator includes a worked example with hand-checkable arithmetic.
- Reader corrections are investigated against the source tables; confirmed errors are fixed and the fix is noted.
What we don't do
- We don't estimate state and local taxes unless the page explicitly says so and names the tables.
- We don't account for tax credits, itemized deductions, or special situations (e.g., self-employment tax uses different rules — see our dedicated calculators).
- We don't give advice. These are estimates for planning and curiosity. For filing decisions, use IRS publications or a tax professional.
Worked example: marginal brackets
Single filer, $85,000 salary, 2026 tax year, standard deduction $16,100:
| Step | Math |
|---|---|
| Taxable income | $85,000 − $16,100 = $68,900 |
| 10% bracket | $12,400 × 10% = $1,240 |
| 12% bracket | ($50,400 − $12,400) × 12% = $4,560 |
| 22% bracket | ($68,900 − $50,400) × 22% = $4,070 |
| Total federal tax | $9,870 |
Effective rate: $9,870 ÷ $85,000 ≈ 11.6% — even though the filer's marginal rate is 22%.