Methodology and sources
Where the numbers come from
Nothing in these calculators is typed from memory. Each constant traces to a primary source, published by the IRS or the statute itself:
| What | Source |
|---|---|
| 2026 brackets, standard deduction | Rev. Proc. 2025-32, sections 3.01 and 3.14 |
| AMT exemption, phaseout, 28% breakpoint | Rev. Proc. 2025-32, sections 4.10 and 4.11 |
| Capital gain breakpoints | Rev. Proc. 2025-32, section 4.03 |
| Supplemental withholding (22% / 37%) | Publication 15, section 7 |
| 83(b) 30-day window | Code section 83(b); Treas. Reg. 1.83-2 |
| ISO / NSO treatment | Code sections 421, 422 and 83 |
| QSBS tiers, $15M cap, $75M assets | 26 U.S.C. 1202 as amended by Pub. L. 119-21 |
How each calculator works
Every tool is a pure function of the inputs. The arithmetic runs in your browser and nothing is sent to a server. Ordinary tax is computed by stacking the 2026 brackets; capital gains are stacked on top of ordinary income at the 0/15/20% breakpoints; AMT compares the tentative minimum tax with the regular tax you would otherwise owe. Where a choice is unavoidable (a single year, one sale, one vesting tranche) the assumption is stated on the page.
How numbers are entered
Fields accept digits only, one decimal point, and ignore grouping as you type. The decimal separator is a period and
the thousands separator is a comma, the US convention: 40,000.25 is forty thousand and a quarter. A comma
with one or two digits after it is read as a European decimal (40,5 becomes 40.5), but mixing both
conventions in one field is the fastest way to get a wrong result, so the field reformats on blur and rejects anything
that is not a number.
What these estimates do not include
- State tax beyond the flat rate you type in, because state rules rarely follow federal treatment for equity pay.
- The 3.8% net investment income tax, except where noted in the QSBS calculator.
- Credits, phaseouts of other benefits, and the payroll-tax consequences of wage income.
- Minimum tax credit recovery in later years, which materially changes ISO outcomes.
- Multi-year planning: spreading exercises, harvesting, or charitable strategies.
Editorial policy
Pages are written and maintained by the 2026 editorial desk of this site, with every calculator reviewed against the primary sources above. We do not publish sponsored reviews of tax software, and no calculator is gated behind a form. Corrections are welcome through the contact page and are applied to the source documents listed here.
Not tax advice
These tools are educational. They cannot account for your full return, your state, or your equity plan documents. For a decision with real money at stake, such as an exercise worth more than your emergency fund, a QSBS sale or an 83(b) filing, confirm the figures with a CPA or tax attorney before you act.