Model a multi-year Roth conversion ladder against the alternative of waiting for RMDs at 73. The calculator handles bracket-fill optimization, IRMAA premium tiers, and after-tax balance comparison.
The Roth conversion decision is one of the highest-leverage retirement-planning choices you'll make. Convert too little and you take a 24%+ tax hit on RMDs starting at 73. 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 runs the full ladder. You provide your traditional balance, your current marginal rate, and your expected RMD-era marginal rate. It returns a year-by-year conversion plan that "fills the bracket" — converting just enough each year to use up your current bracket without spilling — and shows the after-tax outcome at age 90 both ways: convert now, or wait and take RMDs.
The IRMAA tier math is the gotcha most calculators ignore. A Roth conversion of $100k in 2026 can push your MAGI past the IRMAA tier 1 threshold ($212k MFJ for 2026), adding ~$840 to your annual Medicare Part B premium for the year. That's a 0.84% real tax on the conversion that doesn't show up in your marginal bracket. The calculator surfaces this and shows the break-even point where the IRMAA cost outweighs the conversion savings.
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). Convert during the low-income gap, pay tax at 12% or 22%, and dodge 24%+ on the same dollars when RMDs hit. The calculator models this scenario explicitly.
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 — Set your current and projected marginal brackets. If you're retired and in the 12% bracket today, but at 73 you expect to be in the 24% bracket from RMDs + SS, the conversion math is heavily in favor of converting now. If you're in the same bracket either way, conversions are mostly a wash (slight edge for converting if you have heirs in a higher bracket).
Step 3 — Review the year-by-year ladder. The tool returns a 5–15-year schedule, with the optimal conversion amount each year to fill your bracket without spilling. Track when your traditional balance hits zero, when your Roth balance peaks, and what your RMDs look like in each scenario.
Enter your traditional IRA / 401(k) balance, current tax bracket, and projected RMD tax bracket. The tool shows the optimal annual conversion amount to fill your current bracket without spilling into the next one.
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 $96,950 (2026), so you convert ~$47k 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 — at $212k MFJ for 2026, the first IRMAA tier adds $74/month to your Part B premium. The IRMAA hit is based on your MAGI from 2 years prior, so a conversion in 2026 affects your 2028 Medicare premiums. The calculator factors this in and shows the IRMAA-adjusted break-even.
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.