Methodology
What our numbers mean, and what they don’t.
Everyday calculators are planning estimates with methods you can read on each page. Interactive calculations process your inputs in your browser; the values you type are not sent to our server. Initial pages contain precomputed illustrative defaults. The anonymous daily page-view counter sends a random navigation event ID, not calculator values. See our privacy and advertising policy.
100 topics, 500 planning modes, 20 categories
Each topic has five working modes: a detailed baseline calculator, a target-value reverse solver, a one-input comparison, a multi-point sensitivity table, and a full two-scenario comparison. They share a calculation model but perform different planning operations. Only the 100 topic pages are eligible for search indexing; the 400 advanced-mode URLs remain usable but carry noindex and are excluded from the sitemap. The mode count is not a claim of 500 unrelated mathematical formulas.
All inputs are editable. Default values are illustrative, not current market prices, quotes, recommendations or predictions. No live exchange rates, insurance quotes, property assessments or investment returns are fetched.
Tax and paycheck scope
The original income tax and take-home pay calculators share a year- and state-aware wage-tax engine. It estimates annual tax liability, not exact payroll withholding. Paycheck planning tools that request a withholding percentage use the rate you enter instead. Tax-reserve and withholding-gap tools use your own liability estimate; they do not determine state rules or safe-harbor payments.
- Tax years 2026 (default) and 2025. Parameters last reviewed October 22, 2026.
- One W-2 employee. Married filing jointly assumes a non-earning spouse.
- Federal standard deduction only, filers under 65. No dependents, credits, itemized deductions, capital gains or other income.
- Optional traditional employee 401(k) deferral up to the under-50 limit; no catch-up contributions.
- Social Security up to the annual wage base and Medicare including the Additional Medicare Tax.
- Full-year residents only. Local income taxes and state payroll programs (such as Washington paid leave and WA Cares premiums) are excluded.
Supported state wage-tax cases (10)
Alaska, Florida, Nevada, New Hampshire, Pennsylvania, South Dakota, Tennessee, Texas, Washington, Wyoming.
Every other state can be selected, but is marked unsupported. For those states we show federal and payroll tax only and withhold the combined total and net pay, rather than treating state tax as zero.
Tax parameters checked against official sources
Checked October 22, 2026. These are the parameters used by our limited, one-earner wage model, not a certification of a complete tax return. Official IRS, SSA and state links are listed below. Future-year changes are not applied to earlier years.
| Parameter | 2026 | 2025 |
|---|---|---|
| Standard deduction — single | $16,100 | $15,750 |
| Standard deduction — married filing jointly | $32,200 | $31,500 |
| Traditional employee 401(k) limit — under 50 | $24,500 | $23,500 |
| Social Security wage base — per employee | $184,500 | $176,100 |
Employee Social Security: 6.2% up to the annual wage base. Medicare: 1.45% of all wages plus 0.9% above $200,000 (single) or $250,000 (joint) for annual liability. Employers start Additional Medicare withholding above $200,000 regardless of filing status; this is one reason our annual result is not an exact paycheck.
| Rate | Single | Married filing jointly |
|---|---|---|
| 10% | $12,400 | $24,800 |
| 12% | $50,400 | $100,800 |
| 22% | $105,700 | $211,400 |
| 24% | $201,775 | $403,550 |
| 32% | $256,225 | $512,450 |
| 35% | $640,600 | $768,700 |
| 37% | Over $640,600 | Over $768,700 |
| Rate | Single | Married filing jointly |
|---|---|---|
| 10% | $11,925 | $23,850 |
| 12% | $48,475 | $96,950 |
| 22% | $103,350 | $206,700 |
| 24% | $197,300 | $394,600 |
| 32% | $250,525 | $501,050 |
| 35% | $626,350 | $751,600 |
| 37% | Over $626,350 | Over $751,600 |
Supported state wage-tax cases: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming — no state individual tax on modeled W-2 wages in 2025–2026; Pennsylvania — 3.07% of gross wages, no state standard deduction, employee 401(k) deferrals still taxable. Credits, exclusions, local taxes and separate state payroll premiums are not modeled. All other states are unsupported, not assumed to have zero tax.
Open the income-tax calculator to select year and state and inspect the accompanying warnings.
Official tax sources
- IRS — 2025 federal tax brackets
- IRS — 2026 brackets and 2025–2026 standard deductions (OBBBA)
- Social Security Administration — annual wage bases and payroll rates
- IRS — Additional Medicare tax thresholds
- IRS — 2025–2026 employee retirement contribution limits
- Alaska Department of Revenue — individual income tax FAQ
- Florida Department of Revenue — tax information for new residents
- Nevada Department of Taxation
- New Hampshire — no W-2 wage income tax; I&D repeal
- South Dakota Department of Revenue — tax facts
- Tennessee Department of Revenue — Hall income tax repeal
- Texas Comptroller — state taxes
- Washington Department of Revenue — income tax
- Wyoming Department of Revenue
- Pennsylvania — personal income tax, 3.07%, no standard deduction
Everything else
- Compound interest
- Annual rate converted to an equivalent monthly rate; deposits at the end of each month; 0% handled exactly.
- Loan and mortgage
- Standard fixed-rate amortization. Mortgage adds property tax, insurance, HOA and optional PMI below 20% down.
- Retirement
- Monthly compounding to retirement age, deflated by your inflation setting, with a withdrawal-rate heuristic (4% by default).
- Salary and hourly
- Hourly wage times hours per week times paid weeks per year.
- BMI
- CDC adult formula and categories. A screening measure, not a diagnosis.
- Unit conversions
- Exact NIST factors; US customary volumes; temperature via Kelvin.
Each calculator page lists its own sources and assumptions under “How this is calculated”.
Not advice
Results are estimates for general planning and education. They are not tax, legal, financial or medical advice. For decisions with real consequences, confirm with a qualified professional or the official agency.