Roth Conversion Window Calculator 2026
How much can you convert without crossing your target tax bracket? Compare converting nothing with your planned taxable conversion, including a separate illustration of Medicare costs two years later and this conversion's five-year clock.
Last updated: October 30, 2026
2026 conversion tax → 2028 Medicare planning illustration
Federal tax uses published 2026 brackets. A 2026 conversion normally affects 2028 Medicare premiums. The Medicare amounts below hold the published 2026 schedule constant: ILLUSTRATION - NOT OFFICIAL, not 2028 rates or a forecast.
The highlighted amount combines costs in two different years: 2026 federal income tax and one illustrated 2028 Medicare premium year. It is not a same-year tax bill or a lifetime cost. Taxable Social Security, deduction and credit phase-outs, AMT, NIIT, state tax, conversion basis and future investment results are not modeled. Educational estimate, not advice.
What changes if you convert?
| Measure | No conversion | Planned conversion | Difference |
|---|---|---|---|
| Taxable conversion | $0.00 | $25,000.00 | $25,000.00 |
| 2026 ordinary taxable income | $80,000.00 | $105,000.00 | $25,000.00 |
| 2026 ordinary federal income tax | $12,312.00 | $17,812.00 | $5,500.00 |
| 2026 IRMAA MAGI | $100,000.00 | $125,000.00 | $25,000.00 |
| 2028 annual IRMAA · illustration | $0.00 | $1,148.40 | $1,148.40 |
The illustrated Medicare boundary
The starting MAGI band is ≤ $109,000. After the planned conversion it is > $109,000 to ≤ $137,000. These are published 2026 bands used only to illustrate 2028.
| Conversion room before the next IRMAA cliff · illustration | $9,000.00 |
|---|---|
| Next IRMAA cliff starts at MAGI · illustration | $109,001.00 |
| Extra annual IRMAA at that cliff · illustration | $1,148.40 |
This conversion's five-year clock
| Conversion period begins | January 1, 2026 |
|---|---|
| Conversion period ends | December 31, 2030 |
| Conversion period completed | January 1, 2031 |
You have reached age 59½ on the conversion date. The age exception generally removes the 10% early-distribution tax on later withdrawals of converted principal; the separate Roth earnings qualified-distribution rule still applies.
The conversion clock is separate from the Roth earnings qualified-distribution clock. A completed conversion period does not by itself make all earnings tax-free. Withdrawal taxes and penalties are not computed.
Published 2026 federal bracket ceilings
Source: Rev. Proc. 2025-32 §4.01, Tables 1–4. These ceilings use ordinary taxable income after deductions. They are not MAGI thresholds.
| Rate | Single | MFJ / qualifying surviving spouse | Head of household | MFS |
|---|---|---|---|---|
| 10% | $12,400.00 | $24,800.00 | $17,700.00 | $12,400.00 |
| 12% | $50,400.00 | $100,800.00 | $67,450.00 | $50,400.00 |
| 22% | $105,700.00 | $211,400.00 | $105,700.00 | $105,700.00 |
| 24% | $201,775.00 | $403,550.00 | $201,750.00 | $201,775.00 |
| 32% | $256,225.00 | $512,450.00 | $256,200.00 | $256,225.00 |
| 35% | $640,600.00 | $768,700.00 | $640,600.00 | $384,350.00 |
| 37% | No upper ceiling | No upper ceiling | No upper ceiling | No upper ceiling |
FAQ
Does the tax bracket limit how much I am legally allowed to convert?
No. The displayed room is a planning ceiling for your selected federal bracket, not a legal conversion cap. Dollars above the ceiling are taxed through the higher brackets rather than causing all earlier income to be taxed again at the new rate.
Why do ordinary taxable income and IRMAA MAGI have separate fields?
Federal tax brackets use taxable income after deductions. IRMAA normally uses AGI plus tax-exempt interest. A taxable conversion increases both in this fixed-baseline model, but the two starting amounts need not match. We do not recalculate deductions, taxable Social Security or other income-dependent items.
Are the displayed 2028 Medicare charges official?
No. A 2026 conversion normally affects 2028 premiums. The Medicare figures here explicitly hold the published 2026 thresholds and surcharges constant as an illustration. They are not official 2028 amounts or a forecast.
What if some of my IRA conversion is after-tax basis?
Enter only the taxable conversion amount determined using your IRA records and Form 8606. This calculator does not determine the pro-rata taxable share or the gross amount you can transfer.
Does every conversion have its own five-year clock?
Yes. For a calendar-year 2026 conversion, the separate conversion period begins January 1, 2026 and ends December 31, 2030. An early withdrawal of the taxable converted amount may owe the 10% additional tax unless an exception applies, including reaching age 59½. Roth earnings have a separate qualified-distribution rule.
Is this a long-term recommendation to convert?
No. The comparison shows incremental 2026 ordinary federal tax and one illustrated premium year two years later. It does not model future tax brackets, investment returns, RMDs, estate outcomes, state taxes or every interaction on your return. It is an educational estimate, not advice.
Methodology
2026 ordinary-income brackets — IRC §1(j)(2); Rev. Proc. 2025-32 §4.01, Tables 1–4, 2025-45 I.R.B. 695. The IRS revenue procedure states: “For taxable years beginning in 2026, the tax rate tables under § 1 are as follows”. Table 3 includes “Over $50,400 but not over $105,700” and “$5,800 plus 22% of the excess over $50,400”. The page lists every published ceiling used. Qualifying surviving spouses use Table 1 with joint filers; head of household and MFS use their own tables. The model uses a continuous bracket walk, not the IRS tax-table lookup. Equality stays in the lower bracket; only dollars above a ceiling enter the next bracket.
Taxable conversion — IRC §408A(d)(3)(A)(i), (C); IRS Publication 590-A, chapter 2, “Conversions,” “Income.” The statute requires inclusion of “any amount which would be includible were it not part of a qualified rollover contribution”. Pub. 590-A states: “These amounts are normally included in income on your return for the year that you converted them from a traditional IRA to a Roth IRA.” Enter only the taxable portion of a qualifying 2026 IRA-to-Roth conversion. Nontaxable basis and the Form 8606 pro-rata calculation are outside scope. This is conversion planning, not an annual Roth contribution-limit calculation; conversion eligibility is not subject to the regular Roth contribution MAGI limit.
Two different starting incomes. Ordinary taxable income is entered after deductions, without preferential-rate capital gains or qualified dividends. IRMAA MAGI is entered separately as AGI plus tax-exempt interest. The model assumes each taxable conversion dollar increases each entered baseline by one dollar; deductions are held fixed and already used. It does not determine unused deduction room, additional taxable Social Security, AGI-based deduction or credit phase-outs, AMT, NIIT, state tax, withholding or penalties. If the conversion changes those items, obtain a full-return calculation. Tax difference = bracket tax on (ordinary taxable income + taxable conversion) minus bracket tax on ordinary taxable income. Target-bracket room = max(0, selected ceiling − starting ordinary taxable income). The top bracket has no upper ceiling; a zero room is not a legal prohibition on converting.
Medicare lookback — Social Security Act §1839(i), 42 U.S.C. §1395r(i)(4)(B)(i), and §1860D-13(a)(7). SSA's “Your Tax Return” guidance explains that 2026 premiums generally use 2024 tax-year income, and states: “Your MAGI is your total adjusted gross income and tax-exempt interest income.” Accordingly a taxable conversion in 2026 normally affects 2028 premiums, not 2026 premiums. The Part B statute specifies income from “the second calendar year preceding the year involved”. The Part D statute links the income-related adjustment to the Part B income determination.
2028 illustration, not official 2028 amounts — CMS, November 14, 2025, “2026 Medicare Parts A & B Premiums and Deductibles.” The CMS fact sheet supplies the published 2026 thresholds and Part B/D monthly surcharges. We reuse the existing IRMAA module's published schedule unchanged solely as a planning illustration for 2028. Individual ceilings are $109,000 / $137,000 / $171,000 / $205,000, with the top tier beginning at $500,000; joint ceilings are $218,000 / $274,000 / $342,000 / $410,000, with the top tier beginning at $750,000. Special MFS uses $109,000 and an inclusive top-tier start of $391,000. Living apart all year can allow the individual table after SSA attestation (POMS HI 01120.060). Monthly Part B surcharges are $0 / $81.20 / $202.90 / $324.60 / $446.30 / $487.00; Part D surcharges are $0 / $14.50 / $37.50 / $60.40 / $83.30 / $91.00. Standard Part B and actual drug-plan premiums cancel from this difference and are not added. Extra annual IRMAA = 12 × selected covered people × the difference in selected-part monthly surcharges. No coverage means no surcharge. Coverage and filing status are assumed unchanged; both selected people have the same parts for the entire premium year. Appeals, SSA-44 determinations and partial-year enrollment are not modeled. No unpublished 2028 premium or inflation assumption is used.
Both constraints. The maximum taxable conversion that stays within both the selected tax ceiling and the starting illustrated IRMAA tier is the smaller of their remaining dollar rooms. Without Medicare coverage, only the tax ceiling constrains this output. At the highest IRMAA tier there is no higher tier in this schedule. A multi-tier conversion pays the full difference from the starting tier to the resulting tier, not just the first cliff. “Tax + one year of extra IRMAA” adds a 2026 tax cost to one illustrated 2028 premium-year cost; it is not a same-year bill, a lifetime comparison, an investment forecast or advice to convert.
Conversion five-year clock — IRC §408A(d)(3)(F), §72(t); IRS Publication 590-B, chapter 2, “Distributions of conversion and certain rollover contributions within 5-year period.” Pub. 590-B states: “A separate 5-year period applies to each conversion and rollover.” It starts with the first day of the conversion tax year. A calendar-year 2026 conversion therefore has a period of January 1, 2026 through December 31, 2030, completed January 1, 2031. Withdrawing the conversion's taxable amount within that period can trigger a 10% additional tax unless an exception applies, including attaining age 59½ by the distribution date. The qualifying conversion itself is exempt under §408A(d)(3)(A)(ii); cash withheld or not converted can be a different distribution. This clock is separate from the qualified-distribution earnings clock under §408A(d)(2)(B), which depends on the first Roth contribution tax year and a qualifying event. Reaching the displayed completion date alone does not make all earnings tax-free. No withdrawal tax, penalty or earnings is computed.
Input constraints and rounding. Each money input is nonnegative, capped at $10,000,000 and rounded independently to the nearest whole dollar; $0.50 rounds up. Empty, invalid and negative money values become zero. Age accepts decimal years, rounded to two decimal places and bounded from 0 to 120; 59.50 means age 59½ on the conversion date. Taxes and annual premium differences display cents. Unsupported filing, bracket or coverage choices normalize to the documented defaults. Only 2026 conversion tax is modeled. All sources were accessed October 30, 2026; the latest final Pub. 590-A/590-B mechanics apply without importing their prior-year numerical limits.
Sources: Rev. Proc. 2025-32 §4.01, Tables 1–4 (2025-45 I.R.B. 695); IRC §§1(j)(2), 408A(d)(2)–(3), 72(t); IRS Publications 590-A/590-B; CMS November 14, 2025 fact sheet for 2026; Social Security Act §§1839(i), 1860D-13(a)(7); SSA POMS HI 01120.060 — accessed October 30, 2026 — accessed October 2026Last updated: October 30, 2026 · Sourced to IRS, CMS and SSA guidance; awaiting owner acceptanceContinue with OBBBA Tax Center