Roth Conversion Calculator

Between retirement and age 73 — when required minimum distributions begin — many retirees have an unusually low tax rate. Converting traditional IRA or 401(k) dollars to Roth during this window means paying a modest rate now to avoid a higher forced rate later. This calculator shows you the tax cost, the projected RMD impact, and the estimated lifetime benefit of a conversion strategy.

Results are estimates using 2026 federal income tax brackets and standard deductions. State income taxes, capital gains rates, and Social Security taxation thresholds are not modeled. The 15-year RMD horizon assumes a single uniform distribution period; actual RMDs follow the IRS Uniform Lifetime Table each year.

Why retirees convert: the golden window

For most people, the lowest-tax years of their life are between retirement and age 73. Wages stop. Income typically drops. The standard deduction — $32,200 for a married couple in 2026, plus another $3,300 if both are over 65 — shelters a meaningful amount of income from tax entirely.

But that window closes when required minimum distributions begin. At age 73 (or 75 if born in 1960 or later), the IRS requires you to withdraw a percentage of your traditional IRA each year, whether you need the money or not. On a $1M IRA, year-1 RMD is about $37,700. On a $1.5M IRA, it's $56,600. Add that to Social Security and pension income, and many retirees who thought they were in the 12% bracket land in the 22% or 24% bracket — where they'll stay for the rest of their lives.

A Roth conversion moves money from the future high-rate environment into the current low-rate window. You pay tax now, at your current rate, in exchange for tax-free growth and no future RMDs from that money.

How to size a conversion

The goal is usually to fill up your current tax bracket — convert just enough each year to use up the remaining room in the 12% or 22% bracket without crossing into 24%.

A couple with $60,000 in pension + Social Security income, a $32,200 standard deduction, and a $3,300 senior deduction has taxable income of about $24,500. The top of the 12% MFJ bracket in 2026 is $100,800. They have room to convert up to $76,300 before crossing into the 22% bracket. Converting $50,000-$70,000/year is a reasonable target.

RMD age and SECURE 2.0

The SECURE 2.0 Act (2022) changed RMD start ages based on birth year:

• Born 1951–1959: RMDs begin at age 73.
• Born 1960 or later: RMDs begin at age 75 — two more years of the golden window.

SECURE 2.0 also eliminated Roth 401(k) lifetime RMDs starting in 2024 (§ 325). If you have a Roth 401(k), you no longer need to roll it into a Roth IRA to avoid RMDs.

Year-1 RMDs are calculated by dividing your December 31 prior-year balance by an IRS-published divisor. At age 73, the Uniform Lifetime Table divisor is 26.5, meaning you must withdraw about 3.8% of your balance. By age 80 the divisor is 20.2, meaning about 5%.

Source: IRS Publication 590-B, Uniform Lifetime Table (T.D. 9930, effective 2022).

Roth conversions and Medicare (IRMAA)

Medicare Part B premiums in 2026 are $202.90/month for most retirees — but they jump if your income crosses the IRMAA thresholds. IRMAA uses your income from two years earlier, so a large 2026 conversion affects your 2028 premiums.

Source: Kiplinger 2026 IRMAA brackets / CMS. Extra annual cost is per person — a couple pays double. IRMAA applies to Part D premiums separately.

IRMAA is a "cliff" surcharge — $1 over a threshold triggers the full surcharge. A $137,000 MAGI single filer gets hit with $2,435/year in extra premiums; $136,999 pays nothing extra. Staying below an IRMAA tier can be worth adjusting a conversion by a few thousand dollars.

Roth conversions and heirs

A Roth IRA has no lifetime RMDs. When you die, your heirs inherit the account and must draw it down within 10 years under the SECURE Act — but those distributions are tax-free. Contrast this with a traditional IRA, where heirs pay income tax on every distribution at their own marginal rate. For accounts you expect to pass on, converting now essentially pre-pays the tax at your (likely lower) rate instead of your heirs' rate.

1. IRS Rev. Proc. 2025-32 — 2026 tax brackets, standard deductions, senior deductions
2. IRS Publication 590-B — RMD Uniform Lifetime Table (T.D. 9930)
3. Kiplinger — 2026 IRMAA brackets and Part B/D surcharges
4. SECURE 2.0 Act (2022) — § 107 RMD age changes, § 325 Roth 401(k) RMD elimination

Tax values verified against 2026 IRS guidance (Rev. Proc. 2025-32). RMD divisors from IRS Pub 590-B Uniform Lifetime Table. IRMAA from CMS / Kiplinger. Values current as of April 2026.