Roth Conversion Calculator for Married Couples

Enter your combined income and pre-tax balance to find your 2026 conversion sweet spot — how much to convert, at what marginal rate, whether you'd cross the IRMAA cliff, and how years of conversions now shrink your future RMD burden.

Why Roth conversions are a couples-specific strategy

Two spouses with significant pre-tax retirement balances face a compounding problem: both will have required minimum distributions (RMDs) starting at age 73 or 75,¹ and those RMDs stack on top of Social Security and pension income. The result is often a combined AGI well above the $218,000 IRMAA Tier 1 threshold — triggering roughly $2,296/year in Medicare Part B + Part D surcharges for the couple.²

The Roth conversion window is the period between when you stop earning wages and when RMDs begin. For a couple retiring in their early 60s with RMDs starting at 73–75, that's often a 10–15 year window to convert pre-tax dollars to Roth at today's bracket rates — permanently reducing the future RMD load and potentially avoiding IRMAA surcharges for the rest of your lives.

Unlike single filers, married couples face the IRMAA cliff at a point that sits below the top of the 22% bracket. The 22% bracket extends to $243,600 AGI for MFJ in 2026, but IRMAA Tier 1 starts at $218,000.²³ That $25,600 gap is a common trap: couples who convert to fill their tax bracket discover two years later that they've triggered $2,296 in Medicare surcharges that year.

The IRMAA cliff in detail

IRMAA (Income-Related Monthly Adjustment Amount) uses a two-year lookback: your 2026 income determines your 2028 Medicare premiums. The 2026 Tier 1 threshold for married couples filing jointly is $218,000 MAGI (based on 2024 income).² Crossing it costs each enrollee an extra $81.16/month in Part B plus $14.50/month in Part D — about $1,148/year per person, $2,296/year for a couple. It's a cliff: crossing by $1 costs the same as crossing by $50,000.

For Roth conversion planning, treat $218,000 as your hard ceiling unless you've explicitly decided the long-term bracket savings outweigh the two-year Medicare surcharge. Run the math both ways — the calculator above shows both the IRMAA-safe scenario and the full-bracket scenario side by side.

Coordinating conversions across two spouses

RMDs are per-person. A couple where one spouse has $1.2M in a traditional 401(k) and the other has $80K faces a very different problem than a couple with $640K each. The heavier-balance spouse has the larger RMD problem — and converting from that account first gives you the highest marginal reduction in future Medicare surcharges per dollar of tax paid.

Also consider staggered retirement: if Spouse A retires at 62 and Spouse B works until 66, the window where income drops low enough to create meaningful conversion headroom is shorter. Conversions make sense when combined taxable income falls into a range where bracket headroom exists — usually after both spouses have left the workforce.

When to act

The conversion window has a closing date. Every year you don't convert, the pre-tax balance continues growing tax-deferred — and so does the eventual RMD. A couple who waits until age 70 to start conversions has 3–5 fewer years than one who starts at 65. The calculator above shows a simplified multi-year projection — not growth-adjusted, so take it as a floor estimate of the benefit, not a ceiling.

One more reason to act in lower-income years: both tax brackets and IRMAA thresholds are indexed for inflation, but they don't always keep pace with portfolio growth. Pre-tax balances earning 6–7% annually will compound faster than the thresholds inflation-adjust, meaning the RMD problem gets harder to solve the longer you wait.

CouplesAdvisorMatch is a referral service, not a licensed advisory firm. We may receive compensation from professionals in our network. Content is for informational purposes only and does not constitute financial, tax, or investment advice.