Methodology

Last reviewed: October 11, 2026.

Our process

Standard formulas. We use the formulas lenders, the IRS and researchers use (e.g. the amortization formula, Mifflin-St Jeor for calorie needs, the U.S. Navy body fat method). Each calculator page shows its formula.
Automated tests. The math behind every calculator is covered by automated unit tests that check results against published examples, including the IRS tax rate tables in Rev. Proc. 2025-32 and the California FTB 2026 rate schedules. Tests run on every change.
Official sources. Tax figures come from primary sources (IRS, SSA, state revenue departments) and are cited on each page.
Annual review. Federal and state tax figures are updated each year as agencies publish them (usually October–January), and each tax page shows the tax year and review date.

2026 tax data

Federal brackets and standard deduction ($16,100 single / $32,200 joint / $24,150 head of household): IRS Rev. Proc. 2025-32.
Social Security wage base $184,500; Social Security 6.2%, Medicare 1.45% (+0.9% over $200,000): SSA.
401(k) employee limit $24,500 (+$8,000 catch-up at 50+): IRS.
QBI deduction thresholds $201,750 / $403,500: IRS Rev. Proc. 2025-32 §4.26.

State sources

Federal sources

Simplifications

Paycheck estimates compute full-year 2026 tax and divide it across pay periods using the standard deduction. Employers use IRS Publication 15-T withholding tables and your W-4, so actual withholding can differ slightly. Local income taxes are not included. Each page lists its specific assumptions.

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