Methodology & Sources

Every formula the calculators run and every figure they use, with the primary source for each. Tax year 2026. Data last verified: June 10, 2026.

Estimates, not tax advice. This is a simplified planning model. It deliberately ignores anything that can't be modeled honestly without your full tax return.

The calculation, step by step

Net self-employment profit = gross 1099 income − business expenses. Negative results are treated as $0 (losses aren't modeled).
SE tax base = net profit × 92.35%. (IRS Schedule SE rule.)
Self-employment tax = 12.4% Social Security on the base up to $184,500 (2026 wage base) + 2.9% Medicare on the whole base. Additional Medicare Tax = 0.9% on the base above $200,000 single / $250,000 married filing jointly (thresholds are not inflation-indexed).
Half-SE deduction = ½ of the 15.3% portion (the Additional Medicare 0.9% is not deductible).
Approximate AGI = net profit − half-SE deduction. (No other above-the-line deductions are modeled.)
Standard deduction (2026): $16,100 single / $32,200 married filing jointly. Itemizing is not modeled.
QBI deduction (§199A), simplified: 20% of qualified business income, capped at 20% of pre-QBI taxable income. Applied in full when taxable income is below the 2026 thresholds — $201,750 single / $403,500 MFJ — then phased out linearly across the statutory range (to $276,750 / $553,500) and treated as $0 above it. The real rules above the threshold depend on W-2 wages paid, property basis and whether the business is a "specified service" — too individual to fake, so we phase to zero, which is the conservative direction.
Federal income tax: the official 2026 bracket tables (10%–37%) for single and MFJ filers.
State income tax — labeled approximation, computed on approximate AGI (1099) or gross salary (W-2):
- No-tax states (9): $0.
- Flat states: the flat rate × base. State standard deductions/exemptions are ignored.
- Graduated states: an effective rate interpolated linearly from the bottom rate at $0 to the top rate at the top-bracket threshold (single; doubled for MFJ), capped at the top rate. This is intentionally simple and is labeled "approximate" everywhere it appears. It is least accurate in states whose top bracket starts extremely high (New York's 10.9% starts at $25M, so mid incomes show below their real effective rate) or extremely low (Alabama's top rate starts at $3,000, so the approximation reaches the top rate almost immediately — slightly overstating low incomes).
W-2 comparison column: employee-side FICA (6.2% Social Security to $184,500 + 1.45% Medicare + 0.9% additional above the same thresholds), standard deduction, the same 2026 brackets, the same state approximation. Employer benefits are not modeled.
Quarterly set-aside = total annual tax ÷ 4, shown against the official 2026 Form 1040-ES due dates: April 15, June 15, September 15, 2026, January 15, 2027.
Equivalent-salary search: the "your 1099 equals a $X W-2 salary" line is a numerical search (bisection) for the salary whose modeled take-home matches yours — no extra assumptions beyond the formulas above.

What is deliberately NOT modeled

Itemized deductions, credits (child tax credit, EITC, education…), other income (investments, W-2 income alongside 1099 in the same return), retirement contributions (SEP-IRA, solo 401(k)), HSA, health-insurance premium deduction for the self-employed.
State standard deductions, exemptions, credits and special bases; local income taxes (NYC, Maryland counties, Indiana counties, Pennsylvania/Ohio/Michigan municipalities…) — flagged in a footnote on affected state pages.
The full §199A limitation math above the threshold (W-2 wage/UBIA tests, SSTB rules) — replaced by the conservative linear phase-out described above.
Employer benefits in the W-2 comparison: health premiums, 401(k) match, paid leave, unemployment insurance.
The annualized-income method for uneven income (Form 2210 Schedule AI) — mentioned, not computed.

If any of these materially apply to you, your real numbers will differ — that's why every page says estimates, not tax advice.

Every constant and its source

Figure (2026)	Value	Primary source
Federal brackets, single & MFJ	10% → 37% (37% above $640,600 / $768,700)	IRS Rev. Proc. 2025-32, §2.01 tables; cross-checked with Tax Foundation
Standard deduction	$16,100 single · $32,200 MFJ · $24,150 HoH	Rev. Proc. 2025-32 §2.14; IRS newsroom
QBI thresholds / phase-in range	$201,750→$276,750 single · $403,500→$553,500 MFJ	Rev. Proc. 2025-32 §2.26 (extracted from the PDF directly)
SE tax rate & 92.35% factor	15.3% (12.4% + 2.9%) × 92.35% of net profit	IRS — Self-employment tax; Tax Topic 554
Social Security wage base	$184,500	SSA 2026 fact sheet; SSA contribution & benefit base
Additional Medicare Tax	0.9% above $200k / $250k / $125k (MFS)	IRS — Self-employment tax
Employee FICA (W-2 column)	6.2% + 1.45% (+0.9% additional)	IRS Tax Topic 554; SSA 2026 fact sheet
Quarterly due dates 2026	Apr 15 · Jun 15 · Sep 15, 2026 · Jan 15, 2027	2026 Form 1040-ES (extracted from the PDF directly)
Safe harbor	90% current · 100%/110% prior year ($150k AGI trigger)	2026 Form 1040-ES, "General Rule" and "Higher income taxpayers"
All 51 state rates & structures	9 none · 15 flat · 27 graduated	Tax Foundation — State Individual Income Tax Rates, 2026 (every row re-verified June 10, 2026)

The machine-readable dataset behind every page — including per-state rates and per-datapoint source URLs — ships with the site: data/tax-2026.json.

Update policy

Tax figures are refreshed once a year (November–December), when the IRS publishes the next year's revenue procedure, the SSA announces the new wage base, and the Tax Foundation publishes its state survey. Mid-year state changes are folded in when we become aware of them. Every page shows the last-verified date in the footer.

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