See exactly how much you can convert this year to fill your current tax bracket without spilling into the next one — plus IRMAA warnings if you're 63 or older and a long-term breakeven view.
Your tax situation
Filing status
Your age (older spouse if married)
Other taxable income this year (before conversion)
$
Conversion target
Strategy
Conversion amount
$
Growth assumptions
Years until withdrawal
15
Expected annual return
6%
Recommended conversion amount
$0
Fills remaining room in your current bracket
Federal tax on conversion
$0
Marginal rate on conversion
0%
Future value if left in traditional IRA
$0
Where this conversion lands in your 2026 bracket
10%12%22%24%32%35%37%
IRMAA impact check
Not applicable — IRMAA relevant at age 63+
IRMAA uses a two-year lookback — your MAGI this year affects Medicare premiums two years from now.
Long-term value comparison
Scenario
Value at withdrawal
Taxes owed then
Net to you
Key assumption driving this comparison: Roth conversions are most favorable when your current marginal tax rate is lower than your expected rate in retirement (including RMD-driven bracket creep). If you expect a similar or lower rate later, the benefit shrinks or reverses. This calculator assumes your tax rate at withdrawal equals your current marginal rate — adjust your expectations accordingly.
This calculator uses official 2026 IRS federal tax brackets and standard deductions. IRMAA threshold shown is an estimate based on commonly cited 2026 figures — verify current thresholds at CMS.gov before relying on this for Medicare planning. Does not model state taxes, the senior deduction (ages 65+, 2025–2028 only), Net Investment Income Tax, Social Security taxation impact, or the pro-rata rule for mixed pre-tax/after-tax IRAs. Not tax or financial advice.
How this Roth conversion calculator works
This calculator uses the "fill-the-bracket" strategy — the most common approach financial planners recommend for Roth conversions. It calculates how much you can convert from a traditional IRA or 401(k) to a Roth IRA while staying within your current tax bracket, or optionally shows the cost of filling into the next bracket up. It uses official 2026 IRS tax brackets and standard deductions, adjusted by your filing status and other taxable income for the year.
A worked example
A 62-year-old single filer, recently retired, with $20,000 in other taxable income (pension, interest) for the year:
Fill-the-22%-bracket strategy
Other taxable income$20,000
Standard deduction (2026, single)$16,100
22% bracket ceiling (2026, single)$105,700
Room to convert at 22% or lower~$85,700
This retiree could convert roughly $85,700 this year and stay entirely within the 22% bracket — generating meaningful tax-free growth capacity without pushing into the 24% bracket. If this retiree is under 63, IRMAA isn't yet a factor; the two-year Medicare lookback only starts becoming relevant once you're within two years of Medicare eligibility at 65.
The retirement "gap years" — why this window matters so much
The years between retirement and the start of required minimum distributions (RMDs, currently beginning at 73) are often called the "gap years" or "conversion window" — and for good reason. Income typically drops significantly after leaving work, Social Security may not have started yet, and the traditional IRA or 401(k) balance keeps growing untouched. This combination creates the lowest-tax-bracket years many retirees will ever see, making it the single most valuable Roth conversion opportunity in a typical financial life.
Every year this window is left unused, the traditional account balance compounds larger, which means future RMDs will be larger too — potentially pushing retirees into higher brackets involuntarily once RMDs begin. Converting during the gap years is, in effect, trading a known, controllable tax cost today for avoiding an unknown, larger, and mandatory tax cost later.
Frequently asked questions
What is IRMAA and why does it matter for Roth conversions?
IRMAA (Income-Related Monthly Adjustment Amount) is a Medicare Part B and Part D surcharge for higher-income beneficiaries, based on your Modified Adjusted Gross Income (MAGI) from two years prior. A Roth conversion counts as ordinary income and increases your MAGI in the conversion year — a large conversion at age 63 can trigger higher Medicare premiums starting at 65. IRMAA operates as a "cliff": exceeding a threshold by even one dollar triggers the full surcharge for that tier, unlike graduated tax brackets. This makes precise sizing important once you're within two years of Medicare eligibility.
Should I convert everything at once or spread it over multiple years?
Spreading conversions over multiple years is almost always better than converting a large balance all at once. Converting everything in a single year typically pushes a large portion of the conversion into higher tax brackets, since only a limited amount of room exists in each bracket. A multi-year "conversion ladder" that fills a target bracket each year — for example, converting $50,000–$85,000 annually over 5-10 years rather than $500,000 in one year — captures far more of the conversion at lower marginal rates.
What is the pro-rata rule and does it affect my conversion?
If you have both pre-tax (deductible) and after-tax (nondeductible) money across all your traditional IRAs, the IRS treats them as one combined pool for conversion tax purposes — you can't choose to convert only the after-tax portion tax-free. The taxable percentage of any conversion is proportional to the pre-tax percentage of your total IRA balance. This calculator assumes a fully pre-tax balance; if you have nondeductible contributions, consult a tax professional to calculate the pro-rata taxable portion accurately.
Does converting affect how much of my Social Security is taxed?
Yes, if you're already receiving Social Security. Roth conversions increase your provisional income, which determines what percentage of your Social Security benefit is taxable — up to 85% for higher-income recipients. This is a real cost that isn't captured in this calculator's bracket analysis alone. If you're already claiming Social Security, factor in this additional layer of tax impact, or consider converting before you start claiming benefits if your timeline allows it.
When during the year should I execute a Roth conversion?
Many advisors recommend waiting until October or November to execute conversions, once you have a clearer picture of your actual full-year income. A January conversion based on projections can be thrown off by unexpected capital gains, a pension cost-of-living adjustment, or other income surprises later in the year — potentially pushing you into a higher bracket or IRMAA tier than planned. Conversions must be completed by December 31 of the tax year — there's no extension for Roth conversions the way there is for IRA contributions.