Roth Conversion Glidepath Calculator

The Roth Conversion Glidepath Planner (Calculator) maps annual Roth conversions against bracket thresholds, IRMAA cliffs, RMD start dates, and state taxes. Users enter current IRA/401(k) balances, projected returns, pension/SSI start years and estimated benefit amount, medical premiums, and desired cash-flow floor. Outputs: optimal yearly conversion amount, estimated lifetime tax paid vs. deferred, projected Medicare surcharges, and net after-tax retirement income.

Understanding Your Roth Conversion Strategy: A $500,000 IRA Example

Meet Sarah, a 55-year-old professional who has accumulated $500,000 in her traditional IRA through years of diligent saving. She plans to claim Social Security at 67 with an estimated annual benefit of $35,000, has no pension, earns no other income currently, and lives in a state with a 5% income tax. She’s married, filing jointly, and wants to target the 24% federal tax bracket for her conversions.

When Sarah runs the calculator with these inputs, she discovers a compelling conversion strategy. The calculator recommends converting $41,717 annually for 12 years, from age 55 to 66. This represents the sweet spot where she fills up the 24% bracket without triggering any income from Social Security or RMDs. Over these 12 years, she’ll convert the entire $500,000 balance while paying approximately $145,000 in total federal and state taxes.

The timing is crucial. Sarah has a 12-year window before Social Security begins at 67. During these years, she has no other income to compete for space in the lower tax brackets. By converting $41,717 annually, she stays comfortably within the 24% bracket (which tops out at $394,600 for married filing jointly in 2025). More importantly, her modified adjusted gross income remains well below the $206,000 IRMAA (IRMAA stands for Income-Related Monthly Adjustment Amount. It is a government surcharge added to your monthly Medicare Part B (medical insurance) and Part D (prescription drug coverage) premiums if your annual income exceeds certain limits) threshold for married couples, so she avoids Medicare surcharges entirely.

The real power of this strategy becomes clear when we look at the alternative. If Sarah does nothing and lets her IRA grow at 6% annually until age 73, her balance will balloon to approximately $950,000. Her required minimum distribution at that age would be roughly $34,770, and that’s before Social Security. The combination of RMDs plus $35,000 in Social Security benefits pushes her into higher brackets for the rest of retirement, creating a lifetime tax bill that exceeds her conversion strategy by over $200,000.

Sarah’s conversion approach also provides flexibility for her retirement income planning. By moving $500,000 from traditional to Roth, she creates a tax-free income source that won’t count toward IRMAA thresholds or affect Social Security taxation in retirement. Her desired annual retirement income of $80,000 can be drawn more efficiently from a mix of Social Security, Roth distributions, and any remaining traditional IRA funds.

The break-even analysis shows Sarah will recover her conversion taxes within 7 years after RMDs begin at age 73, putting her at age 80. Given typical life expectancy, she has potentially decades of tax-free growth and distributions ahead. More significantly, she’s eliminated the risk of future tax rate increases on her retirement savings and created a valuable estate planning asset, since Roth IRAs pass to heirs tax-free without the same RMD requirements as traditional IRAs.

What makes this strategy particularly powerful is the compounding effect of tax-free growth. The $500,000 Sarah converts will continue growing at 6% annually inside the Roth IRA, but all future growth and distributions come out tax-free. Over a 30-year retirement, this could represent an additional $2 million in tax-free wealth compared to leaving the funds in a traditional IRA where every distribution is taxed as ordinary income.