Plan a multi-year Roth conversion ladder that fills your chosen tax bracket each year. The planner shows the estimated federal tax, state tax and Social Security "torpedo" for each year, flags Medicare IRMAA exposure, and shows the total cost and effective rate.
The Roth conversion decision is one of the highest-leverage retirement-planning choices you'll make. Leaving more money in pre-tax accounts can lead to larger required minimum distributions (RMDs) later. Depending on your birth year, RMDs generally begin at age 73 or 75, and the additional taxable income may affect your tax bracket. Convert too much in a single year and you spill into a higher marginal bracket, push your Medicare premium up via IRMAA, and may even trigger the 3.8% Net Investment Income Tax (NIIT).
This calculator builds the ladder. You provide your traditional balance, your other income this year, your state, your age, your Social Security benefit, the bracket you want to fill, the number of years, and an expected return. It returns a year-by-year conversion plan that "fills the bracket" — converting just enough each year to reach the top of your chosen bracket — with the estimated federal tax, state tax, extra Social Security taxation, total cost, and remaining traditional balance for each year. Future-year IRMAA is flagged but not included in the ladder totals. It does not project a side-by-side comparison against waiting for RMDs.
The IRMAA tier math is the gotcha most calculators ignore. A Roth conversion of $100k in 2026 can push your MAGI above the first IRMAA threshold ($218,000 MFJ for 2026), adding about $974 per enrollee to annual Medicare Part B premiums ($81.20/month in 2026), plus a Part D surcharge. That's an extra cost of about 1% of the conversion per Medicare enrollee (about double that for a married couple who are both enrolled) that doesn't show up in your marginal bracket. Because a conversion affects premiums two years later and those future IRMAA tables are not yet published, the planner flags the exposure but future-year IRMAA is not included in the ladder totals.
Real-world note: most Roth conversions make the most sense in the gap years between retirement (when ordinary income drops) and Social Security claiming (when income jumps back up). Converting during the low-income gap may let you pay tax at a lower rate than the same dollars could face later, when RMDs add to your taxable income. The planner flags these gap years based on your age and your RMD start age.
Step 1 — Enter your traditional balance. Sum of trad IRA + pre-tax 401(k) / 403(b) / 457(b) / TSP + SEP IRA + SIMPLE IRA. NOT Roth IRA, NOT Roth 401(k), NOT HSA (HSA after 65 acts like trad IRA for non-medical, but doesn't trigger RMDs).
Step 2 — Choose the bracket to fill and the number of years. Pick the top of which federal bracket to convert up to (for example 12% or 22%) and how many years to spread conversions over. If you expect to be in a higher bracket later from RMDs plus Social Security, filling a lower bracket now may be worth considering; if you'll be in the same bracket either way, conversions are closer to a wash.
Step 3 — Review the year-by-year ladder. The tool shows the conversion amount for each year, its estimated federal tax, state tax and Social Security torpedo where it applies (IRMAA exposure is flagged, not included in the totals), the total cost, and the remaining traditional balance — plus totals for the amount converted, the all-in tax cost, and the effective rate.
Enter your traditional IRA / 401(k) balance, other income, state, age, Social Security, the bracket you want to fill, and how many years to spread conversions over. The tool shows a year-by-year conversion schedule with its estimated tax, and flags Medicare IRMAA exposure (future-year IRMAA is not included in the totals).
Open the converter →Three reasons. (1) Lock in today's tax rate if you expect higher rates later — for many retirees the gap years before RMDs are the lowest-bracket years they'll ever see. (2) Eliminate RMDs on the converted portion; Roth IRAs have no RMDs during your lifetime. (3) Estate planning: heirs inherit the Roth tax-free and have 10 years to drain it under SECURE Act rules, but no tax bill — vs. a pre-tax IRA where the heir pays ordinary income on every distribution.
Strategy of converting just enough each year to use up your current marginal bracket without spilling into the next one. Example: married couple in retirement with $50k taxable income, the 12% bracket ends at $100,800 (2026), so you convert ~$51k to push to the top of the 12% bracket. The conversion gets taxed at 12% instead of waiting to face 22% (or 24% with future RMDs). Repeat each year until the trad balance is converted or you reach RMD age.
Medicare Part B premiums increase via the Income-Related Monthly Adjustment Amount (IRMAA) at 5 tier thresholds. A Roth conversion increases your MAGI, which can push you into a higher IRMAA tier — above $218,000 MFJ for 2026, the first IRMAA tier adds $81.20/month to each enrollee's Part B premium (plus a Part D surcharge). The IRMAA hit is based on your MAGI from 2 years prior, so a conversion in 2026 affects your 2028 Medicare premiums. The planner flags IRMAA exposure, but because those future-year IRMAA tables are not yet published, future-year IRMAA is not included in the ladder totals.
Each Roth conversion starts its own 5-year clock. Withdraw the converted PRINCIPAL within 5 years and the 10% early-withdrawal penalty applies (regardless of age, with limited exceptions). After 5 years (or age 59½, whichever comes first), the principal is freely withdrawable. EARNINGS on conversions need to satisfy BOTH the 5-year rule for the Roth IRA itself AND age 59½ before they're tax- and penalty-free.
Yes, but you must take your full RMD FIRST before converting any additional amount. The RMD itself can't be converted to Roth — it's a required distribution. You can take the RMD, pay tax on it, and then in the same year convert additional traditional balance to Roth as a separate transaction. Both events show up on your 1099-R for the year.
