The Multi-Year Roth Conversion Planner

This tool runs the Conversion Cost Calculator year by year and returns a complete multi-year schedule. Instead of asking "what does one conversion cost?" it asks "how much should I convert in each year between now and my first RMD, filling low brackets and dodging IRMAA cliffs, to minimize total lifetime tax?" The output is a year-by-year table showing conversion amount, bracket fill, IRMAA impact, and cumulative Roth balance, plus a total-tax-paid comparison against the do-nothing baseline.

Roth conversion planning is fundamentally a multi-year optimization. A single large conversion in year one maximizes compounding but often pushes you into a higher bracket and crosses IRMAA tiers. A series of smaller conversions spread across five to ten years usually comes out ahead because you stay in lower brackets and avoid IRMAA spikes. This tool finds the right trade-off automatically.

Who should use this tool

Pre-retirees and early retirees (roughly ages 55 to 75) with substantial Traditional IRA or 401(k) balances. The "gap years" between retirement and the start of RMDs (age 73 or 75 under SECURE 2.0 §107) are the single highest-value conversion window for most households. This tool quantifies the value and lays out the schedule.

It's also useful for readers modeling what happens if they delay conversions entirely until RMDs force distributions — the tool's "do nothing" baseline shows the total lifetime tax in that scenario, which is almost always higher than even a moderately aggressive conversion ladder.

Walking through the inputs

Starting age and starting balance. Your age today and the current Traditional IRA/401(k) balance you're planning to convert from. The tool will project forward year by year until your first RMD year.

Annual non-conversion income. Wages (if still working), pension, Social Security, and any other ordinary income you expect each year. You can model changes — for example, wages until age 65, then Social Security starting at 67. This establishes the "baseline" that the conversion stacks on top of.

Target bracket fill. The top bracket you're willing to convert into. Most planners use 22% or 24% as the ceiling. You can also choose "IRMAA tier 1" or "IRMAA tier 2" as the constraint if you're on Medicare.

Expected return assumption. The real rate of growth on both the Traditional and Roth side. Default is 5% real; lower assumptions favor conversion now (less compounding benefit, so the tax-rate arbitrage matters more relative to the tax drag).

How to read the result

The schedule table shows, for each year from now until RMD year: the conversion amount, which brackets it fills, the federal tax on the conversion, IRMAA surcharge two years out, end-of-year Roth balance, and end-of-year Traditional balance. The total row at the bottom shows lifetime tax paid under this plan versus the do-nothing baseline.

The tool also produces an "efficiency" figure: total tax paid divided by total converted dollars. Values below 20% are very strong; 20–25% is good; above 30% suggests you're overdoing it — either converting too much or starting too late.

Common mistakes this tool prevents

• Converting too aggressively. Filling the 32% bracket is almost never optimal when you have five years of 22%-bracket room ahead. The planner spreads conversions automatically.
• Missing the IRMAA two-year look-back. A conversion in 2026 affects 2028 Medicare premiums. The planner tracks this year by year.
• Forgetting RMD acceleration from inherited IRAs. If you inherited an IRA, your RMD schedule is set by different rules. The planner doesn't model inherited balances — keep them separate.
• Ignoring the five-year conversion clock for under-59½ converters. Each year's converted principal has its own five-year clock. Withdrawing before the clock matures triggers the 10% penalty. The planner flags any converted amount you'd need to tap within five years.
• Planning without state tax. Some states tax the conversion fully, others exempt it for seniors. Enter your effective state rate to see the real after-tax number.

After you have the schedule

Execute the first-year conversion early in the tax year — converting in January gives eleven extra months of tax-free growth versus December. Re-run the planner every year to update assumptions (your actual income, actual balances, any law changes). Most households will revise their plan at least once over the five-to-ten-year window.

If you're deciding between the Roth 401(k) and Traditional 401(k) at work, the Roth vs. Traditional Comparator answers that separate question.

Worked example: a 62-year-old with a $900,000 Traditional IRA

Consider Patricia, age 62, recently retired from a career as a software architect. She has $900,000 in a Traditional IRA (rolled from a 401(k) at separation), no pension, and is deferring Social Security to age 70 to maximize her benefit. She has $150,000 in taxable savings to cover spending until Social Security starts, and she files single. Her first RMD year is 2039 (age 75 under SECURE 2.0 §107), giving her a 13-year conversion window.

If Patricia does nothing, her Traditional IRA compounds at 5 % real to roughly $1.70M by age 75. Her first RMD (factor 24.6) is about $69,000, landing fully in the 22 % federal bracket. Combined with her Social Security (mostly taxable at her income level), her 2039 taxable income is near $115,000 — comfortably into the 22 % bracket, above the first IRMAA tier (projected 2039 threshold around $120,000 for single filers), and materially above where she'd prefer to be.

The planner recommends converting approximately $55,000 per year for each of years 2026–2032 (seven years, roughly $385,000 total at today's dollars). Each conversion stays within the 12 % bracket given her otherwise low income in the pre-Social-Security years. Total federal tax on the seven-year conversion stream: approximately $46,000 — paid from her taxable savings. By age 70 she has converted about $385,000 plus growth to Roth, leaving roughly $700,000 in Traditional (grown from the reduced base).

From 2033 onward her RMD base is smaller, her RMDs start at age 75 from a smaller balance, and her lifetime tax drops by an estimated $180,000 compared to the do-nothing baseline — net of the $46,000 paid during conversion. The Roth balance, which continues to compound tax-free and has no RMD, is worth approximately $560,000 (in today's dollars) at her age-85 projection, providing a flexible pool for late-retirement spending and a tax-free inheritance for her heirs.

The key insight: Patricia's conversion "arbitrage" is between her 12 % bracket today and her projected 22 % bracket under the do-nothing RMD path. That 10-point spread, compounded across seven years of conversions and 13 years of tax-free Roth growth, is what drives the six-figure lifetime tax saving.