About SelfTaxCalc
Last reviewed
Why this exists
Roughly 60 million Americans work for themselves, and most of them work out their taxes alone. The arithmetic is not conceptually hard, but it is specific: the 92.35% adjustment, the Social Security cap, the half-deduction against AGI, the QBI phase-out, and then a state layer that behaves differently from the federal one. Getting the order wrong produces an answer that looks plausible and is not.
SelfTaxCalc runs that arithmetic properly, for free, with no sign-up and no email capture, for all fifty states and the District of Columbia.
Who writes this
Muhammad Akbar
Founder and engineer, SelfTaxCalc
Builds and maintains the calculators on this site. Every formula here is implemented directly from the IRS's own worksheets — Schedule SE, Form 1040-ES and the Form 1040 instructions — and each figure is traced to the source documents listed below rather than copied from another site.
Stated plainly: SelfTaxCalc produces estimates, not tax advice. No one here is a CPA, an enrolled agent or a tax attorney, and nothing on this site creates a professional relationship. Estimates are a starting point for planning and for a conversation with a professional — they are not a substitute for one.
How the numbers are derived
Calculations follow the order of operations on the IRS forms themselves: net profit, the 92.35% adjustment, self-employment tax, the 50% deduction against AGI, the standard deduction, the §199A QBI deduction with its phase-out, then the federal brackets. State tax is computed separately on state AGI less that state's own standard deduction, because no state allows the federal QBI deduction and almost none allow the federal standard deduction.
The engine behind every calculator on the site is the same one, covered by an automated test suite that checks the federal brackets are contiguous, that no state's bracket table is malformed, that a loss never produces tax, and — specifically — that the federal standard deduction and the §199A QBI deduction never reduce a state bill, which is a mistake this site previously made and has corrected.
How current the 2026 figures are
Tax data on this site is static and versioned, not pulled from a live feed. A person checks it against the source documents and updates it; the review date at the top of this page and on every calculator says when that last happened.
That is slower than an automatic feed would be, and it is the honest description. If a state changes a rate mid-year, the figure here will be stale until it is reviewed — which is exactly why the date is displayed rather than hidden.
What these estimates do not cover
The calculators model a single filer or a married couple filing jointly with self-employment income as the main source. They do not model local income taxes, W-2 wages held alongside freelance work, itemized deductions, the alternative minimum tax, or credits. Where a local income tax exists, it is described on that state's page.
Corrections
Found a figure that is wrong? Tell us and it gets fixed and noted. Corrections are logged, not quietly edited. Write to hello@selftaxcalc.com with the page and the figure you think is wrong, and ideally the source you are comparing it against. See also the full method.
What the federal figures come from
- IRS Revenue Procedure 2025-32 — 2026 inflation adjustments — tax brackets, standard deduction, QBI thresholds.
- IRS Schedule SE instructions — Self-employment tax: the 92.35% adjustment, the Social Security wage base, the Medicare surtax.
- IRS Form 1040-ES — Estimated tax deadlines and the safe-harbour rules used for the quarterly schedule.
- IRS Publication 334 — Tax guide for small business — deductible expenses and net profit.
- IRS Social Security wage base — The $184,500 Social Security cap applied for 2026.