Some gains are free. The question is how many.

The facts, in one place.

Six quotable sentences from the 2026 tables.

1. Long-term capital gains are taxed at 0, 15, or 20 percent depending on where they land once stacked on top of ordinary income. For 2026 the 0 percent band runs to $49,450 of taxable income on a single return and $98,900 on a joint return; the 15 percent band to $545,500 and $613,700.
2. Taxable income is adjusted gross income less deductions; the 2026 standard deduction is $16,100 single and $32,200 joint. The room is the band's top minus taxable ordinary income, and a gain that fits inside it is taxed at zero.
3. A single filer with $50,000 of adjusted gross income has $33,900 of taxable income and $15,550 of room at 0 percent; realizing $20,000 of gain costs $668, because the last $4,450 is taxed at 15 percent.
4. The net investment income tax adds 3.8 percent on investment income above $200,000 of modified adjusted gross income single and $250,000 joint; the thresholds have not been indexed since 2013.
5. Harvesting a gain resets cost basis: the same shares can be bought back the same day, since the wash-sale rule applies to losses, not gains. The gain is real income for every other purpose that year: Medicare premiums two years out, the taxable share of Social Security, and the senior deduction's phase-out.
6. Qualified dividends share the same bands, so they are already in the stack before a harvested gain is added.

The bands.

The three bands and the surtax threshold, both statuses.

How the stacking works.

Long-term capital gains and qualified dividends are taxed by where they land once stacked on top of everything else on the return. Ordinary income fills the taxable-income axis first; the gain sits on top of it and is taxed at 0 percent up to the band's top, 15 percent to the next, and 20 percent beyond. A gain that fits entirely inside the 0 percent band costs nothing in federal tax and raises the cost basis of the shares, which is the whole point of harvesting it.

Two things sit outside the bands. The net investment income tax adds 3.8 percent on investment income above a threshold of modified adjusted gross income that has not moved since 2013. And Medicare premiums two years out are set by adjusted gross income, which the gain joins in full. The calculator draws the bands, the surtax threshold, and the Medicare tiers on one axis so all of it is visible at once.

Methodology.

1. Inputs. Adjusted gross income before the gain, the filing status, and the long-term gain to realize.
2. Taxable ordinary income. Adjusted gross income less the 2026 standard deduction for the status. An itemizer's figure differs by the difference; so does the room.
3. The room. The 0 percent band's top minus taxable ordinary income, never below zero, from the thresholds in the revenue procedure.
4. Tax on the gain. The gain split across the bands in order (0, then 15, then 20 percent), plus 3.8 percent on the smaller of the gain and the excess of adjusted gross income including the gain over the § 1411 threshold.
5. Medicare. The tier for adjusted gross income with and without the gain, from the CMS tables; the premium difference is per person, doubled for a joint return.
6. Validation. Four pinned cases: a gain that spans the 0 and 15 percent bands, a joint return with no room and the surtax on the whole gain, a gain with no other income, and a single filer past the 15 percent band's top. A transcription error fails the build.
7. Not modeled. Qualified dividends already in the stack (they shrink the room), short-term gains, collectibles and § 1250 gain, state tax, the alternative minimum tax, the taxable share of Social Security, the senior deduction's phase-out, and carryforward losses. Educational, not advice.

Sources.

1. 1. Internal Revenue Service, Rev. Proc. 2025-32 — 2026 inflation adjustments (tax rate tables § 4.01, capital gains § 4.03, AMT exemptions § 4.10). Every 2026 bracket boundary and base amount for individuals and for estates and trusts; the 0% and 15% capital-gain thresholds; the AMT exemption amounts. Retrieved September 4, 2026; verified September 4, 2026.
2. 2. United States Code (Cornell LII), 26 U.S.C. § 1411 — Imposition of tax (net investment income). The 3.8% surtax; for a trust, the threshold is the dollar amount at which the highest § 1(e) bracket begins; for individuals, $200,000 and $250,000, unindexed. Retrieved September 4, 2026; verified September 4, 2026.
3. 3. Centers for Medicare & Medicaid Services, 2026 Medicare Parts A & B Premiums and Deductibles (fact sheet, November 14, 2025). The Part B standard premium and deductible, the Part A inpatient deductible, and every row of the Part B and Part D income-related adjustment tables. Retrieved September 4, 2026; verified September 4, 2026.
4. 4. United States Code (Cornell LII), 42 U.S.C. § 1395r(i) — Income-related increase in Part B premium (and, by cross-reference, Part D). That the income used is modified adjusted gross income from the return two years before the premium year, and the mechanism of the tiers. Retrieved September 4, 2026; verified September 4, 2026.
5. 5. Internal Revenue Service, Rev. Proc. 2025-32 — 2026 inflation adjustments (§ 4.14 standard deduction; § 4.42 gift exclusion). The standard deduction amounts, the additional amounts for age or blindness, the $19,000 gift exclusion, and the $194,000 non-citizen-spouse exclusion. Retrieved September 4, 2026; verified September 4, 2026.
6. + United States Code (Cornell LII), 26 U.S.C. § 1(h) — Maximum capital gains rate. That net capital gain is taxed at 0, 15, or 20 percent by reference to the taxable income thresholds, stacked above ordinary income.

Revision history.

This tool reads the federal and annual records; their histories are below.

September 5, 2026

Added the senior deduction's phase-out rate (6 percent of MAGI over the threshold), which the widow's penalty and QCD tools apply.

September 4, 2026

First release of the annual numbers record and page for 2026, and of the IRMAA tool built on its Medicare section: plan and IRA limits from Notice 2025-67, HSA figures from Rev. Proc. 2025-19, Social Security figures from the Federal Register notice, Medicare premiums and both income-related tables from the CMS fact sheet, the standard deduction and gift exclusion from Rev. Proc. 2025-32, and the senior deduction from the IRS's OBBBA guidance.

September 4, 2026

First release of the federal income-tax record for 2026 and the trust income-tax tool: the estates-and-trusts table, the single and joint tables for comparison, capital-gain thresholds, AMT exemptions, the § 1411 trust threshold rule, and the § 642(b) exemptions, all from Rev. Proc. 2025-32 and the Code.

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