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
- California: FTB Tax News: 2026 Indexing (rate schedules, standard deduction, exemption credits); EDD: 2026 contribution rates (SDI 1.3%)
- Texas: Texas Comptroller: taxes (no personal income tax)
- Florida: Florida Dept. of Revenue: Florida has no personal income tax
- New York: NY DTF: personal income tax rates and 2026 rate reduction; NY DTF: withholding tax rate changes; NY DTF: standard deduction amounts (statutory; page shows 2025, amounts not inflation-indexed)
- Pennsylvania: PA Dept. of Revenue: personal income tax (3.07%)
- Illinois: IDOR IL-700-T: 2026 Illinois withholding tables ($2,925 allowance); IDOR FY 2026-15: What’s new for Illinois income taxes
- Ohio: EY Tax News: states that lowered income tax rates in 2026 (Ohio H.B. 96); Ohio Dept. of Taxation: 2026 withholding percentage method
- Georgia: Georgia DOR: Employer’s Tax Guide (2026, updated Sept 2026); Georgia HB 463 (signed 2026)
- North Carolina: N.C.G.S. §105-153.7 (rate schedule); NCDOR: North Carolina standard deduction; NCDOR: tax rate schedules
- Michigan: Michigan Treasury: 4.25% rate for 2026 tax year; Michigan 2026 Income Tax Withholding Guide (Form 446)
Federal sources
- IRS Rev. Proc. 2025-32 (2026 brackets & standard deduction)
- IRS newsroom: 2026 inflation adjustments
- IRS Rev. Proc. 2025-32 §4.26 (2026 QBI thresholds $201,750 / $403,500)
- IRS: Self-employment tax (Social Security and Medicare taxes)
- SSA: 2026 contribution and benefit base ($184,500)
- IRS: 401(k) limit $24,500 for 2026
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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