US salary calculator methodology (federal, 2026)

W-2 employee — per-paycheck model

Federal income tax withholding uses Publication 15-T (2026), Worksheet 1A (Percentage Method, automated payroll). Supports Form W-4 2020+: Step 2 (two-jobs checkbox), Step 3 (annual credits), Step 4(a) other income, Step 4(b) deductions, Step 4(c) extra withholding, and the “exempt” flag. When Step 2 is NOT checked, the annual wage is adjusted by $8,600 (single/MFS/HOH) or $12,900 (MFJ) before lookup; when checked, no adjustment (halved bracket widths on dedicated schedules).

FICA (2026)

• Social Security: 6.2 % employee / 6.2 % employer, annual wage base $184,500 (SSA).
• Medicare: 1.45 % employee / 1.45 % employer, no cap.
• Additional Medicare 0.9 % — employer must withhold on cumulative wages paid by this employer above $200,000 (employee liability thresholds: $250k MFJ, $125k MFS, $200k single/HOH).
• FUTA: 0.6 % effective on the first $7,000 of wages per year (assumes standard state credit).

Net → gross (W-2)

For a target net pay per period, we binary-search on gross pay so the gross → net function matches, holding W-4 and YTD inputs fixed.

1099 contractor / self-employed — annual estimator

• SE tax (Schedule SE): 92.35 % of net profit × (12.4 % Social Security up to combined $184,500 with W-2 wages + 2.9 % Medicare + 0.9 % Additional Medicare on the portion over the filing-status threshold).
• If net profit < $400, no SE tax is owed (§1402(b)(2)).
• ½ SE tax is an above-the-line deduction (Schedule 1).
• Standard deduction 2026 (post-OBBBA): single / MFS $16,100; MFJ $32,200; HOH $24,150.
• 2026 progressive federal brackets (Rev. Proc. 2025-32): 10 % / 12 % / 22 % / 24 % / 32 % / 35 % / 37 %.
• Suggested quarterly payment (Form 1040-ES) = ¼ × (SE + IT) — simplified, no safe-harbor logic.

Bonuses and supplemental wages

Separate tool (different URL): mandatory flat federal withholding of 22 % on supplemental wages, and 37 % on the portion above the $1,000,000 supplemental-YTD threshold, plus FICA and optional employer cost. This is NOT a third mode inside the salary calculator.

Out of scope (v1)

State and local income taxes, AMT, NIIT 3.8 %, full QBI (§199A), §401(k) / IRA / HSA / FSA / §125 pre-tax buckets, CTC / EITC / credits, nonresident alien (§1441) rules, post-OBBBA 2025+ deductions (tips $25k, overtime $12.5k / $25k, car loan interest, senior $6k), SUI/SUTA, multi-state apportionment. Educational only — not tax advice and not a substitute for payroll software.