Roth Conversions in Retirement: Should You Convert, and How Much?

Your required minimum distribution cannot be converted. That is because the IRS requires you to distribute the RMD before any additional IRA money is eligible for rollover or conversion. For example, if your RMD is $33,000 and you then convert another $15,000 from a fully pretax IRA, the $33,000 comes out first and the additional $15,000 moves to Roth. You generally recognize $48,000 of IRA income that year, before other tax effects. The RMD remains taxable even if you do not convert.

RMDs generally begin at age 73 for people born in 1951–1959 and 75 for those born in 1960 or later. Older birth cohorts follow earlier rules, and some employer plans have special deferral rules. See the Roth conversion rules guide for the account details.

Original Roth IRA owners have no lifetime RMDs. That can make conversions attractive, but it does not prove the conversion tax is worthwhile. First estimate the RMDs you are actually trying to reduce using the MRM RMD calculator.

Perhaps future RMDs would force more income than you plan to spend. Perhaps one spouse would face higher taxes after the other dies. Or perhaps adult children might inherit a large pretax IRA during their highest-earning years. Tax diversification and withdrawal flexibility can also matter.

Those are reasons to test converting, not promises of savings. If withdrawals would be taxed at a lower rate later, or the IRA is likely to go to charity, paying conversion tax now may be a poor trade. A large RMD by itself is not a calculation of avoidable tax.

Name the problem first: future taxes, the surviving spouse, heirs, or flexibility. Then test whether the conversion actually improves it.

Today you pay the incremental income tax plus any lost deductions or benefits. Later you may benefit from smaller taxable IRA withdrawals, different inheritance treatment, or greater tax flexibility. A lower RMD is not automatically an equal-sized tax saving.

On this intentionally simple $10,000 comparison, a $2,332 current tax bill is more than $1,200 at a hypothetical future 12% rate. Even a hypothetical 22% future rate does not settle lifetime value. Growth, timing, tax-payment resources, future law and heirs can reverse the conclusion.

Married households also need a survivor test. The surviving spouse may have much of the same IRA money but face single-filer tax brackets and Medicare thresholds. If the couple plans to spend little of the IRA, the heirs’ eventual tax treatment may matter more than the couple’s RMDs.

Depending on the household, the additional conversion income can change:

• Federal ordinary income tax and, if relevant, state income tax.
• Taxable Social Security. Additional income can make a larger share of benefits taxable until the taxable portion reaches its limit.
• Capital gains. More ordinary income can occupy room where long-term gains would otherwise have qualified for a favorable rate.
• Marketplace health insurance credits. Conversion income can reduce or eliminate income-tested premium assistance before Medicare.
• Medicare IRMAA. Higher conversion-year income can affect Part B and Part D premiums in a later Medicare year.
• Income-tested deductions. In 2026, this can include the enhanced deduction for people 65 and older.
• Net investment income tax. The conversion isn’t itself net investment income, but its effect on modified AGI can expose other investment income to NIIT.

Not all these costs apply to everyone. Some are current-year effects, while Medicare IRMAA typically works from tax information from two years earlier. Compare the complete household picture with and without the conversion.

One often-missed 2026 cost is the temporary enhanced senior deduction. Qualifying people age 65 or older may deduct up to $6,000 each for 2025–2028, subject to an income phaseout. For a married couple with both spouses qualifying, each spouse’s $6,000 amount is reduced by 6% of joint MAGI above $150,000. That can make the next $10,000 reduce the combined deduction by $1,200, rather than $600, while both amounts remain within the phaseout range.

The next-$10,000 test asks what the additional conversion really costs and what specific future result might justify that cost.

Couple A: Both 62, with Marketplace health insurance

Couple A: Married, both age 62, with $1.2 million in pretax accounts, $80,000 of ordinary income (also assumed to be their Marketplace MAGI), no Social Security yet, and Marketplace coverage. Assume an otherwise allowable $6,000 annual premium tax credit as a case input, not a guaranteed credit amount.

Their $10,000 conversion generates $1,200 more ordinary federal income tax under the stated assumptions. That alone looks manageable.

For 2026 coverage, CMS uses the 2025 poverty guideline of $21,150 for a two-person household in the contiguous states. Its 400% threshold is $84,600. The temporary rule allowing credits above 400% expired after 2025. A conversion from $80,000 to $90,000 MAGI crosses that limit. If the assumed $6,000 credit disappears, the illustrative combined cost is $7,200, not $1,200. IRS premium tax credit rules and CMS’s 2026 Marketplace threshold table establish the eligibility mechanics.

Important: $6,000 is an assumed benefit loss for this example, not a calculated typical subsidy. Actual credit amounts depend on location, ages, plan prices, family details and coverage months; advance credits may also need reconciliation on the tax return.

For this couple, testing a smaller conversion or waiting until Medicare deserves more consideration than simply filling the 12% bracket.

Couple B: Both 67, on Medicare, before RMDs

Couple B: Both age 67, married, on Medicare, Social Security delayed, $1.5 million in pretax accounts, and $170,000 AGI consisting of ordinary income before conversion.

The 2026 joint standard deduction is $32,200, with another $3,300 because both are 65 or older. At $170,000 MAGI, each spouse loses $1,200 of the $6,000 enhanced deduction. Their combined enhanced deduction is therefore $9,600, leaving $124,900 taxable income.

With a $20,000 conversion, MAGI rises to $190,000. Each spouse’s enhanced deduction falls to $3,600, or $7,200 combined. Taxable income rises to $147,300, an increase of $22,400. Since this extra taxable income is in the 2026 22% bracket, their illustrative incremental federal tax is $4,928, before Medicare or other interactions. The phaseout added $528 to a simple 22%-of-$20,000 calculation.

Medicare adds a delayed cost to model: a 2026 conversion will generally be considered in the tax information used for 2028 IRMAA, subject to SSA’s usual two-year lookback and any applicable adjustments. Official 2028 premium brackets are not yet available. The IRMAA sizing guide shows how to use an explicitly assumed threshold.

This couple has reasons to analyze future RMDs and survivor taxation, but $4,928 today is not itself evidence of a lifetime saving.

Retiree C: Single, 74, already taking RMDs

Retiree C: Single, age 74, with an $850,000 traditional IRA at the end of 2025. Using the age-74 Uniform Lifetime Table divisor of 25.5, the illustrative 2026 RMD is about $33,333. It must be distributed before any additional eligible conversion.

Assume AGI of $115,000 including that RMD and any taxable Social Security, with the taxable Social Security portion already at its 85% maximum. After the $16,100 standard deduction, the $2,050 age addition, and a $3,600 remaining enhanced senior deduction, taxable income is $93,250.

A further $10,000 conversion raises AGI to $125,000, reduces the enhanced senior deduction to $3,000, and lifts taxable income to $103,850. That adds $10,600 to taxable income, producing $2,332 incremental federal tax at 22%, excluding possible future IRMAA and other effects.

Conversion is permitted after the RMD, but the $2,332 only makes sense if future personal, survivor or heir outcomes justify it. Permission to convert is not proof that doing so helps.

For example, capital-gain harvesting may use favorable long-term gain rates in a low-income year. A regular IRA distribution might better meet spending needs. Either can be preferable to paying conversion tax, depending on the facts.

Charitable retirees have another option. A properly executed qualified charitable distribution (QCD) after age 70½ can count toward an RMD without adding that amount to taxable income. See IRS Publication 590-B. A QCD is not interchangeable with Roth conversion, but it may address the income problem the conversion was meant to solve.

Compare what the household keeps after taxes and benefits, including how you finance the conversion tax. A projection should test different future tax rates, spending, longevity and heirs, not pretend to know one future path.

Equally, keeping Medicare premiums low at all costs is not automatically optimal. Crossing an IRMAA threshold may be reasonable if the future benefit is more valuable. The MRM IRMAA tradeoff guide explains that separate calculation.

After RMDs begin, conversion remains an option. What changes is its price.

Before deciding, I want three things on the same page: the problem the conversion solves, its total cost today, and the plausible result if nothing is converted. Paying tax sooner only deserves consideration when the comparison holds up.