Research and validation
How PaycheckCalc estimates take-home pay
By Barron Hansen, Founder ยท Updated May 28, 2026
Paycheck math is a deterministic pipeline. PaycheckCalc starts with gross salary, applies pre-tax deductions (401(k), HSA, itemized substitution for standard deduction), computes federal taxable income against the 2026 bracket schedule from IRS inflation-adjustment guidance, layers FICA (Social Security up to the $184,500 wage base, Medicare on every dollar, the 0.9% Additional Medicare Tax above $200,000 single or $250,000 MFJ), runs state income tax through that state's bracket or flat-rate schedule from the state revenue department, and adds any supported city or county local tax plus state-administered payroll programs (SDI, PFML, FLI, TDI). The site's content-freshness date reflects when the underlying tax-engine data and prose were last reviewed against primary sources for bracket figures and supported jurisdictions. The body sections below walk through each layer of the calculation, name the data sources, and call out known limitations. The methodology is open by design: every primary source linked here is publicly available from a government tax authority.
Federal income tax computation
Federal income tax in 2026 uses a seven-bracket progressive schedule: 10%, 12%, 22%, 24%, 32%, 35%, and 37%. Brackets apply to taxable income, which is gross salary minus pre-tax deductions (401(k), HSA, qualified benefits) and the standard deduction ($16,100 single, $32,200 MFJ, $24,150 head of household). Each bracket taxes only the slice of income inside its range. The calculator pulls bracket thresholds, rates, and standard-deduction figures from the tax-engine federal config, which mirrors IRS inflation-adjustment guidance for tax year 2026. The federal Alternative Minimum Tax is not modeled; the engine assumes regular-tax treatment, which holds for the salary range the calculator targets.
FICA: Social Security and Medicare
FICA is the payroll tax that funds Social Security and Medicare. Social Security is 6.2% on wages up to the 2026 wage base of $184,500; income above the cap is not subject. Medicare is 1.45% on every dollar with no cap. The Additional Medicare Tax of 0.9% applies to wages above $200,000 single ($250,000 MFJ); employers withhold once year-to-date wages cross $200,000 regardless of filing status, with household-level reconciliation on the federal return. The calculator uses SSA wage-base and IRS Additional Medicare thresholds linked under Primary Sources.
State income tax structure
State structure splits into three classes. Nine states have no broad-based personal income tax on wages. Sixteen apply a single flat rate to every wage dollar. The remaining twenty-six jurisdictions, including DC, use progressive bracket schedules ranging from sub-three-percent floors to top rates above 10%. The calculator stores each state's schedule in the tax-engine state config files, sourced from each state's department of revenue or taxation. Some states layer income-conditioned surtaxes on top of the regular schedule: California's Mental Health Services Tax (+1% above $1 million) and Massachusetts's Millionaire Surtax (+4% above the indexed threshold) are wired as separate surtax fields.
Local tax layers
Local income tax applies in jurisdictions concentrated in seven states. Pennsylvania has near-universal Earned Income Tax. Ohio runs municipal income tax in 600-plus jurisdictions via RITA and CCA. Kentucky cities and counties levy the Occupational License Tax. Michigan has 24 cities including Detroit. New York City and Yonkers levy resident income tax. Maryland layers a county tax in every county and Baltimore City. Indiana has a county income tax in every county. The calculator currently models 68 jurisdictions including NYC, Philadelphia, Detroit, Louisville, Pittsburgh, Cleveland, Cincinnati, and Columbus.
Wired state payroll programs
Eleven states administer employee-funded payroll programs that show up as per-paycheck pay-stub lines: California SDI, Colorado FAMLI, Hawaii TDI, Massachusetts PFML, Maine PFML, Minnesota PFML, New Jersey SUI and FLI, New York PFL and SDI, Oregon Paid Leave, Rhode Island TDI, and Washington PFML. Each has its own rate, wage cap, and effective date. The calculator surfaces these as comma-joined labels on supported state pages so prose can reference them inline. Rates and caps refresh alongside each tax-year update, with a verification timestamp recorded per program.
Known limitations
The calculator targets a steady-state W-2 salary for a single primary employer. Not modeled: custom W-4 elections beyond filing status, supplemental wage handling for bonuses and stock vests, multi-state employment and nonresident credits, reciprocity scenarios, the federal Alternative Minimum Tax, self-employment tax, capital gains, and state-specific quirks like New Jersey's 401(k) state-deductibility treatment (the engine understates NJ state tax when a 401(k) deferral is modeled). Known partial-coverage gaps per state surface via the partialCoverageGaps array and render as a pendingDataNotes callout on supported state pages.
Update cadence
Federal brackets, FICA wage bases, and retirement contribution limits update when the IRS publishes the relevant revenue procedure (typically October to November of the prior calendar year). State updates follow each state's legislative session, with most rate changes effective January 1. Local rate changes follow municipal budget calendars and can land mid-year. The content-update date constant records the most recent review and propagates to every page's byline. Corrections submitted via the contact form are reviewed within a few business days.
Frequently asked questions
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Reviewed
How This Page Is Reviewed
Methodology updates are reviewed before publication and again whenever major federal, state, or local withholding assumptions change.
Reviewed by
PaycheckCalc Research Desk
Last reviewed
2026-05-28