Who makes this
I have worked as an independent contractor for over ten years. Every time one of these questions came up (what a 1099 offer is really worth, what to charge, how much to set aside for taxes), I could not find an answer I trusted. The ones I found were vague, contradicted each other, or came from someone trying to sell me something.
So I built the tool I wanted: one where every figure traces to a primary source, so you can check it instead of taking my word for it. That is the whole point of the site.
The site is free, with no login and no paywall on the calculators. It runs no third-party trackers and shows no cookie banner; the only analytics is a cookieless, privacy-preserving count of page views.
I am not an accountant or a tax professional, and nothing here is a credential. What I can offer instead is a method you can inspect for yourself, which is the rest of this page.
How every number is checked
Two kinds of number go into these tools, and they are held to two different standards.
Tax constants are law, or published by the government: the federal brackets, the standard deduction, the Social Security wage base, the self-employment and Medicare rates, the estimated-tax due dates. Each one is read from its primary source when the tool is built, never from memory, and stored alongside the exact document it came from and the date it was checked. Recalled figures are wrong often enough to matter. When this tool was built, the Tax Foundation's published 2026 brackets did not match Revenue Procedure 2025-32 for the top married-filing-jointly threshold. The tool uses the primary source: that bracket begins at $768,700.
The engine is covered by more than 230 automated tests, and a green suite is the ship gate: nothing goes live until every test passes. Where it can, the suite anchors to externally published values rather than to the tool's own output. The federal brackets, for instance, are checked against the cumulative "The Tax Is" amounts printed in the Revenue Procedure, so a passing test proves the number is right, not merely that it has not changed.
Guards are fault-injected to prove they bite. After a test is written to catch a bad constant, the constant is deliberately corrupted to confirm the test fails, then restored. A guard that does not fail when the number is wrong is a false sense of safety, not a pass.
The whole chain is hand-verified end to end against IRS mechanics for at least one full scenario, every step shown. You can read one worked out line by line on each calculator page. Doing this the first time surfaced two real bugs that the all-green tests had missed.
What is a sourced fact, and what is not
This distinction is the core of the promise, so it is worth stating plainly. Two things on these pages are estimates, not constants:
- State income tax is a flat effective rate, not your bracket. It comes from a published table: a state's income tax collections per person divided by its per-capita personal income. That makes it an average across taxpayers, with local and city income taxes excluded. It is a reasonable planning figure, not an IRS constant, and it is labeled that way wherever it appears.
- Your own inputs are starting points, not sourced facts. Billable utilization, weeks worked, business expenses and the like are assumptions you own. Their defaults are editorial judgement and carry no citation. Change them until they describe your year.
Each calculator also lists the specific things its model leaves out, near the bottom of its own page.
Sources
Each constant was verified against the primary source on the date shown.
- 2026 federal brackets, standard deduction and QBI thresholds: IRS Revenue Procedure 2025-32, read from the PDF at irs.gov/pub/irs-drop/rp-25-32.pdf. Verified 2026-07-15.
- Social Security wage base ($184,500) and the payroll and self-employment tax rates: Social Security Administration, ssa.gov/oact/cola/cbb.html. Verified 2026-07-15.
- Additional Medicare Tax (0.9%) thresholds: statutory, under IRC sections 3101(b)(2) and 1401(b)(2); the IRS "Questions and Answers for the Additional Medicare Tax" page confirms them in plain language. Verified 2026-07-15.
- Estimated-tax due dates: IRS 2026 Form 1040-ES, "Payment Due Dates" table, at irs.gov/pub/irs-pdf/f1040es.pdf. Verified 2026-07-22.
- State effective rates: Tax Foundation, Facts & Figures 2026, Table 12 (FY2024); D.C. from Table 13 (FY2023); per-capita income from US BEA, SAINC1 per-capita personal income, 2024 annual; effective rate = income tax collections per capita ÷ per-capita personal income. Verified 2026-07-15.
- Health cost defaults: KFF, the 2025 Employer Health Benefits Survey (employer contributions) and the 2026 average benchmark marketplace premium (self-paid default).
Estimates for planning, not tax advice
These tools are built carefully and checked against primary sources, but they cannot see your whole return. They are for planning, not filing. For a decision that goes on a tax form, talk to a CPA or an enrolled agent.