IRMAA-Aware Roth Conversion Calculator (2026)
For Medicare-eligible retirees, Roth conversions can trigger IRMAA surcharges — up to $13,872/year extra for a couple — that hit two years later. This calculator finds your conversion sweet spots: the maximum you can convert before each IRMAA cliff, and the scenarios where crossing a tier is still worth it.
The IRMAA cliff: why $1 over the line costs $1,148/year per person
Unlike income tax brackets (which only apply incrementally to income above the threshold), IRMAA is a cliff surcharge. Cross $218,000 MAGI as a married couple and you owe the full Tier 1 surcharge on all your Medicare premiums — not just the excess. The extra dollar of conversion income can cost a couple $2,296/year.
The IRMAA cliffs fall at completely different income levels than tax bracket thresholds, so the right Roth conversion amount isn't simply "fill the 22% bracket." It's often "fill to whichever comes first — the next tax bracket or the next IRMAA tier."
2026 IRMAA tiers (based on 2024 MAGI)
| MAGI — Single | MAGI — MFJ | Part B surcharge/mo | Part D surcharge/mo | Annual extra/person |
|---|---|---|---|---|
| ≤ $109,000 | ≤ $218,000 | $0 | $0 | $0 |
| $109,001–$137,000 | $218,001–$274,000 | $81.20 | $14.50 | $1,148/yr |
| $137,001–$171,000 | $274,001–$342,000 | $202.90 | $37.50 | $2,885/yr |
| $171,001–$205,000 | $342,001–$410,000 | $324.60 | $60.40 | $4,620/yr |
| $205,001–$500,000 | $410,001–$750,000 | $446.30 | $83.30 | $6,355/yr |
| ≥ $500,000 | ≥ $750,000 | $487.00 | $91.00 | $6,936/yr |
Source: Kiplinger — 2026 Medicare IRMAA Brackets and Surcharges. Base Part B premium: $202.90/month.
When crossing an IRMAA tier is still worth it
IRMAA is a temporary cost — it applies only while your MAGI stays above the threshold. A conversion is a one-time income event. If you convert $50,000 over an IRMAA tier in 2026, the surcharge applies to 2028 premiums only (assuming your income drops back below in 2027). The break-even is usually straightforward:
- Cost of crossing the tier: Tier 1 surcharge × 1 year × number of enrollees (e.g., $2,296 for a couple)
- Tax savings from the conversion: conversion amount × (expected future bracket − current bracket)
Example: $50,000 converted above IRMAA Tier 1, saving 10 points of bracket (22% now vs. 32% at RMD) = $5,000 in lifetime tax saved vs. $2,296 one-year IRMAA hit. Net: +$2,704. In most bracket-differential scenarios, crossing one tier is justified.
What's usually not justified: a multi-year conversion plan that keeps you in Tier 2 or higher for 5–8 years. Cumulative IRMAA at $5,770/yr per couple adds up quickly.
The two-year lookback trap for new retirees
IRMAA for 2026 is based on your 2024 MAGI. If you retired in 2024 but had W-2 income for most of that year, your 2026 Medicare premiums may be in IRMAA territory even with zero conversions. Once you're in IRMAA anyway, crossing to the next tier becomes the only relevant comparison — not "should I avoid IRMAA" but "should I pay Tier 2 instead of Tier 1 for one year."
File SSA Form SSA-44 if a life event (retirement, loss of a spouse's income, business sale) reduced your current income below what your 2024 return shows. SSA can recalculate IRMAA using current-year income.
Why IRMAA planning requires multi-year modeling
The optimal Roth conversion strategy coordinates:
- IRMAA thresholds (two-year lookback means decisions made this year affect premiums two years from now)
- Tax bracket boundaries (which are on taxable income, not MAGI)
- Social Security income (which stacks on top of conversion income)
- State income taxes (California and New York effectively add 9–13% to the cost of conversions)
- RMD trajectory (how large will forced withdrawals be at 73, 75, 80?)
A spreadsheet can handle one year. A specialist advisor runs the full 10-year model — which years to convert heavily, which years to hold back, and when the lifetime NPV tips decisively one way.
Frequently asked questions
What is IRMAA and how does it affect Roth conversions?
IRMAA (Income-Related Monthly Adjustment Amount) is a Medicare surcharge applied when your MAGI exceeds certain thresholds. In 2026, single filers over $109,000 and married couples over $218,000 pay extra Part B and Part D premiums ranging from $1,148 to $6,936 per person per year. Roth conversions count as ordinary income and can push your MAGI into a higher IRMAA tier, triggering surcharges two years later due to the lookback rule.
What are the 2026 IRMAA thresholds for Roth conversions?
The 2026 IRMAA tiers (based on 2024 MAGI) are: Tier 1 at $109,000 single / $218,000 MFJ ($1,148/yr per person extra); Tier 2 at $137,000/$274,000 ($2,885/yr); Tier 3 at $171,000/$342,000 ($4,620/yr); Tier 4 at $205,000/$410,000 ($6,355/yr); Tier 5 at $500,000/$750,000 ($6,936/yr). Source: CMS 2026 Medicare costs.
Should I stay under the IRMAA threshold when doing a Roth conversion?
Not always. IRMAA is a cliff surcharge, not a bracket — crossing Tier 1 costs a couple $2,296/year for one year. If your conversion saves $5,000–$10,000 by converting at 22% instead of 32% at RMD time, crossing the tier is still profitable by thousands of dollars. Staying under every IRMAA threshold often means under-converting by a significant amount. The calculator above shows the break-even for your specific situation.
How does the IRMAA two-year lookback work for Roth conversions?
IRMAA for 2026 is calculated from your 2024 MAGI, not your current income. Conversions in 2026 affect 2028 Medicare premiums. If you had high W-2 income in 2024 and retired in 2025, your 2026 premiums may already be in an IRMAA tier with zero conversions — in which case staying just below a tier is irrelevant and you should focus on whether crossing to the next tier is worth it.
Can I appeal an IRMAA surcharge triggered by a Roth conversion?
IRMAA appeals via SSA Form SSA-44 are allowed for qualifying life events — retirement, divorce, or death of a spouse — but not for a one-time Roth conversion. If a large conversion pushed your MAGI into a higher tier, the surcharge applies to that lookback year and cannot be appealed on the basis of the conversion itself.
How do I find the optimal Roth conversion amount around IRMAA tiers?
Enter your filing status, Medicare enrollees, other MAGI, and IRA balance into the calculator above. It identifies every IRMAA tier ceiling and tax-bracket top applicable to your situation and flags the largest conversion that stays within a favorable rate + IRMAA combination. A fee-only advisor then models this across 5–10 years, adjusting for Social Security timing, RMD growth, and state taxes.
Related reading
Have a specialist run your full IRMAA + bracket analysis
This calculator maps the thresholds. A fee-only advisor models your actual MAGI trajectory across 5–10 years — including Social Security timing, RMD projections, state tax, and multi-year IRMAA management. Free match, no obligation.