The bracket has room in it. The question is how much.

The facts, in one place.

Six quotable sentences from the 2026 tables.

1. A Roth conversion is ordinary income in the year it is done. For 2026 the 22 percent bracket runs from $50,400 to $105,700 of taxable income on a single return and from $100,800 to $211,400 on a joint return; the 24 percent bracket runs to $201,775 and $403,550.
2. Taxable income is adjusted gross income less deductions; the 2026 standard deduction is $16,100 single and $32,200 joint. The room in a bracket is the bracket's top minus taxable income.
3. A single filer with $100,000 of adjusted gross income has $83,900 of taxable income and $21,800 of room at 22 percent; converting $30,000 costs $6,764, because the last $8,200 is taxed at 24 percent.
4. Medicare premiums are set by adjusted gross income from two years earlier, in tiers with hard edges: the first tier begins above $109,000 single and $218,000 joint, and one dollar over moves the whole premium up a step for the year.
5. Because the tiers apply to adjusted gross income and the brackets to taxable income, a conversion that fits neatly in a bracket can still cross a Medicare tier; the two lines sit $16,100 apart on a single return.
6. Conversions cannot be undone: since 2018 there is no recharacterization. The room is measured once, with the year's income known, and the conversion is sized to it.

The brackets.

The brackets a conversion fills, both statuses, as the revenue procedure states them.

How the room works.

A conversion moves money from a traditional IRA to a Roth IRA and is taxed as ordinary income in the year it happens. Because the brackets are steps, the useful question is not whether to convert but how much fits before the next step: the space between taxable income and the top of the current bracket. Fill it and stop, and every converted dollar is taxed at today's rate; go past it and the rest is taxed at the next.

The second line is Medicare. Premiums two years from now are set from this year's adjusted gross income, in tiers with hard edges, and a conversion counts. A conversion that fits the bracket can still cross a tier, and the cost of crossing is the whole step for a year, for each spouse on Medicare. The calculator draws both lines on one axis so the smaller of the two rooms is visible.

Methodology.

1. Inputs. Adjusted gross income before the conversion, the filing status, and the amount to convert.
2. Taxable income. Adjusted gross income less the 2026 standard deduction for the status. An itemizer's taxable income differs by the difference; so does the room.
3. The room. The current bracket's upper bound minus taxable income, from the 2026 tables in Rev. Proc. 2025-32.
4. Tax on the conversion. The ordinary tax on taxable income plus the conversion, minus the ordinary tax without it, so a conversion that spans two brackets is taxed at both rates.
5. Medicare. The tier for adjusted gross income with and without the conversion, from the CMS tables the IRMAA calculator uses; the premium difference is per person, doubled for a joint return.
6. Validation. Four pinned cases, including a conversion that spans the 22 and 24 percent brackets, and a check that each status's brackets are contiguous and rising. A transcription error fails the build.
7. Not modeled. Qualified dividends and capital gains stacking, the net investment income tax, the senior deduction and other phase-outs, state income tax, the taxation of Social Security benefits, and the five-year rules on the Roth side. 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. § 1 — Tax imposed; § 1(e) estates and trusts; § 1(j) 2018-and-later rate structure made permanent. That estates and trusts have their own compressed rate schedule, and the four rates it uses. Retrieved September 4, 2026; verified September 4, 2026.
3. 3. 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.
4. 4. United States Code (Cornell LII), 26 U.S.C. § 642(b) — Deduction for personal exemption (estates and trusts). The $600 / $300 / $100 fiduciary exemption amounts. Retrieved September 4, 2026; verified September 4, 2026.
5. 5. United States Code (Cornell LII), 26 U.S.C. §§ 651–652 and 661–662 — Deduction for distributions; inclusion by beneficiaries. That income a trust distributes (within distributable net income) is deducted by the trust and taxed to the beneficiary instead: the mechanism the comparison illustrates. Retrieved September 4, 2026; verified September 4, 2026.
6. 6. 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.
7. 7. 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.
8. 8. 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.

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.

Canonical address: https://consideratecapital.com/tools/roth-conversion-room