Roth Conversion Calculator 2026: Tax Cost & IRMAA Impact
Figures last verified against official IRS and CMS sources in July 2026.
Quick Answer
Converting a Traditional IRA to a Roth IRA creates fully taxable ordinary income in the year of conversion. In 2026, if the conversion pushes your Medicare MAGI above $109,000 (single) or $218,000 (joint), it triggers a Medicare IRMAA surcharge of $81.20 to $487.00 per month — two years after the conversion year. Always calculate the full cost: income tax + IRMAA impact before converting.
Roth Conversion Calculator 2026
Calculate your upfront tax bill and check if a Traditional-to-Roth IRA conversion triggers a Medicare IRMAA premium surcharge.
Most retirees considering a Roth conversion calculate the immediate income tax bill but forget the "hidden tax" — triggering a higher Medicare IRMAA premium tier two years later. Converting $50,000 in one year can look affordable at 22% tax, but if it pushes your Medicare MAGI over the IRMAA cliff, you could pay an extra $1,000–$5,000 per year in Medicare surcharges for two years straight. We built this free calculator to give you the complete picture in seconds — upfront tax cost, IRMAA surcharge alert, and estimated break-even years.
- Retirees aged 60–72 in a low-income "gap year" between retirement and age 73 (when RMDs begin) who want to convert Traditional IRA funds while in a lower tax bracket.
- Medicare beneficiaries who want to verify a planned conversion will not push their MAGI above the IRMAA surcharge thresholds for Parts B and D.
- Adults doing multi-year "bracket filling" — converting small amounts annually to drain a Traditional IRA into a Roth and reduce mandatory RMDs starting at age 73 or 75.
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How to Use This Roth Conversion Calculator — Step by Step
- Step 1 — Enter your current MAGI before the conversion. Enter your Modified Adjusted Gross Income for the year before adding the conversion amount. This is Line 11 of your most recent Form 1040 plus any tax-exempt interest income. This figure sets your starting point for both tax bracket and IRMAA threshold calculations.
- Step 2 — Enter the conversion amount you are considering. Enter the dollar amount of pre-tax Traditional IRA or 401(k) funds you want to convert to a Roth IRA. The calculator adds this to your base MAGI to compute your new post-conversion MAGI for the year.
- Step 3 — Select your filing status and marginal tax bracket. Choose "Single" or "Married Filing Jointly" and select your current federal income tax bracket. The calculator applies the correct bracket to the conversion amount to compute the exact federal tax owed.
- Step 4 — Review total cost, IRMAA alert, and break-even estimate. The results panel shows your upfront tax bill, whether your new MAGI crosses an IRMAA threshold, the two-year Medicare cost of that surcharge, and the number of years of tax-free Roth growth needed to break even on the conversion cost.
💡 Pro Tip
Always pay conversion taxes using taxable cash from a savings or checking account — never by withholding from the IRA being converted. If you are under 59½, funds withheld to pay taxes are subject to a 10% early withdrawal penalty on the withheld portion. Even if over 59½, using IRA money to pay taxes permanently reduces the amount growing tax-free. Check IRS conversion rules at IRS Roth Comparison Chart.
Why Multi-Year Partial Roth Conversions Are the Best Strategy for Most Retirees
Converting a large Traditional IRA all at once in a single year creates two expensive problems simultaneously: it pushes you into the highest marginal tax bracket on the entire converted amount, and it spikes your Medicare MAGI above IRMAA thresholds — often for two consecutive premium years.
Instead, most retirement tax planners recommend multi-year partial conversions between retirement and age 73 (when RMDs begin). By converting smaller amounts each year — enough to "fill up" the 22% bracket without crossing into 24% or triggering IRMAA — you systematically move money into a Roth at the lowest possible rates over a decade.
The 2026 IRMAA Thresholds — Know the Cliffs Before You Convert
IRMAA surcharges are "cliff" brackets — crossing a threshold by even $1 triggers the entire surcharge for the full year. The 2026 IRMAA Medicare surcharge tiers are:
| MAGI (Single Filer) | MAGI (Joint Filer) | Monthly Part B Surcharge | Annual Extra Cost |
|---|---|---|---|
| ≤$109,000 | ≤$218,000 | $0 (Standard Rate) | $0 |
| $109,001 – $137,000 | $218,001 – $274,000 | +$81.20/month | ~$974/yr |
| $137,001 – $171,000 | $274,001 – $342,000 | +$202.90/month | ~$2,435/yr |
| $171,001 – $205,000 | $342,001 – $410,000 | +$324.60/month | ~$3,895/yr |
| $205,001 – $500,000 | $410,001 – $750,000 | +$446.30/month | ~$5,356/yr |
| >$500,000 | >$750,000 | +$487.00/month | ~$5,844/yr |
Source: CMS Medicare Part B Cost Information. IRMAA surcharges also apply to Part D premiums; the amounts above reflect Part B only. Always check our IRMAA Calculator for the complete Part B + Part D combined surcharge impact.
Real-Life Examples — Roth Conversion Planning in Practice
Donald is single with a current MAGI of $85,000. He wants to convert $20,000 to a Roth IRA in 2026 to reduce future RMDs.
| Input | Value |
|---|---|
| Current MAGI (pre-conversion) | $85,000 |
| Planned Conversion Amount | $20,000 |
| New Post-Conversion MAGI | $105,000 |
| Tax Owed on Conversion (22%) | $4,400 |
| IRMAA Threshold (single, 2026) | $109,000 |
Action Taken: Donald set a reminder to check the IRMAA threshold each year before executing his conversion, since CMS adjusts it annually for inflation.
Sandra is single with a $90,000 MAGI. Her financial advisor recommended converting $60,000 from her Traditional IRA in one year to "get it done quickly."
| Input | Value |
|---|---|
| Current MAGI (pre-conversion) | $90,000 |
| Planned Conversion Amount | $60,000 |
| New Post-Conversion MAGI | $150,000 |
| Tax Owed on Conversion (22%–24%) | ~$14,400 |
| IRMAA Tier Crossed | Tier 2 ($137k–$171k) — +$202.90/month |
What Sandra Should Have Done: Convert $15,000/year for four years instead — staying below the IRMAA cliff each year while still completing the same $60,000 total conversion at a lower effective tax rate.
William and Carol file jointly with a combined MAGI of $160,000. They want to convert enough Traditional IRA funds to reach — but not cross — the 24% bracket and the next IRMAA tier.
| Input | Value |
|---|---|
| Current MAGI (pre-conversion, joint) | $160,000 |
| Top of 22% Bracket (joint, 2026) | $206,700 |
| Next IRMAA Threshold (joint, 2026) | $218,000 |
| Maximum Safe Conversion | ~$46,700 (to stay at $206,700) |
| Tax on Conversion (22%) | ~$10,274 |
Strategy Used: "Bracket filling" — converting the maximum amount that stays within the current tax bracket and below the IRMAA cliff. Recalculated every January for updated IRS and CMS figures.
These are representative examples for educational purposes. Individual results vary based on exact income, investment returns, state taxes, filing status, and specific account balances. Verify your conversion plan with a qualified tax professional before executing any Roth conversion.
Common Roth Conversion Mistakes and How to Avoid Them
Crossing an IRMAA Medicare Surcharge Threshold by a Few Hundred Dollars
IRMAA brackets are strict "cliff" thresholds with no gradual phase-in. If a Roth conversion pushes your single MAGI to $106,001 (just $1 over the 2026 threshold), you incur the full Tier 1 IRMAA surcharge of $81.90 per month ($982.80 per year) for Medicare Part B — plus additional Part D surcharges. This $982 annual cost applies for two full years after the conversion year.
The fix is to leave a $2,000–$3,000 cushion below each IRMAA threshold when planning your conversion amount, to buffer against any income estimation errors. Verify current IRMAA brackets using our Medicare IRMAA Calculator before committing to a conversion.
Paying Conversion Taxes by Withholding from the IRA Being Converted
Many custodians offer to automatically withhold a percentage of the conversion to cover the tax bill. This feels convenient but is mathematically counterproductive. Withheld funds never enter the Roth IRA — they never grow tax-free. If you are under 59½, they are also subject to the 10% early withdrawal penalty on the withheld amount specifically.
The fix is to pay 100% of the conversion tax from outside cash — savings, checking, or a CD — so the entire converted amount enters the Roth and begins compounding tax-free. See IRS guidance at IRS Roth Comparison Chart.
Converting a Large Amount in a Single Year Instead of Spreading Over Multiple Years
Converting $100,000 in one year is not the same as converting $25,000 per year for four years. A single large conversion stacks income, pushing large portions into the 24%, 32%, or 35% brackets — rates you could have avoided by spreading the conversion across lower-income years. Multiple smaller conversions stay in lower brackets and avoid IRMAA cliffs.
The fix is to create a multi-year conversion plan using the "bracket filling" strategy — calculate the maximum safe conversion amount for your current bracket each year, then execute that amount annually starting at retirement.
Converting Traditional IRA Funds When You Expect a Lower Tax Rate in Retirement
A Roth conversion only makes long-term financial sense if you expect to be in the same or higher tax bracket in the future. If you are currently in the 22% bracket and expect to drop to 12% in retirement due to lower income, paying 22% now to avoid 12% later is a net loss — even accounting for tax-free growth.
The fix is to model your expected retirement income using our Retirement Tax Estimator before committing. Also consider that increasing RMDs may push your future bracket higher than expected, which strengthens the case for converting.
Official Government Sources Used in This Tool
| Source Name | What We Used It For | Direct Link |
|---|---|---|
| IRS Publication 590-A — Contributions to IRAs | Roth IRA conversion eligibility rules, income inclusion rules, and the 5-year holding period requirements for converted funds | IRS Publication 590-A |
| IRS Roth Comparison Chart — Conversions vs. Contributions | Official IRS table distinguishing Roth contribution rules from Roth conversion rules, including no-income-limit conversion eligibility | IRS Roth Comparison Chart |
| CMS Medicare Part B Premium & IRMAA Surcharge Brackets 2026 | Official 2026 MAGI thresholds ($109,000/$218,000 baseline) and monthly Part B IRMAA surcharge tier amounts for all five tiers | Medicare.gov Part B Costs |
| SECURE 2.0 Act of 2022 — RMD Age Changes (Section 107) | Updated RMD starting ages to 73 (born 1951–1959) and 75 (born 1960 or later), which directly affects the value of reducing pre-RMD Traditional IRA balances through Roth conversions | SECURE 2.0 Act — Congress.gov |
Seniors Audit is an independent educational platform. We are not affiliated with, endorsed by, or connected to the IRS, CMS, or any government agency, insurance company, or financial services firm. All calculations use official tax code formulas and published IRMAA rates. We do not receive payment for referrals or any action taken by visitors to this site.
Frequently Asked Questions About Roth Conversions
What is a Roth IRA conversion and how does it work?
A Roth IRA conversion is the process of moving pre-tax money from a Traditional IRA, 401(k), or 403(b) into a tax-free Roth IRA. The full amount converted is treated as ordinary taxable income in the year of the conversion. After conversion, all future growth and qualified withdrawals from the Roth IRA are 100% tax-free — for you and for your heirs who inherit the account.
How does a Roth conversion affect Medicare IRMAA premiums?
A Roth conversion increases your Adjusted Gross Income (AGI) on Form 1040, which also raises your Medicare MAGI. Social Security uses MAGI from two years prior to set your Part B and Part D IRMAA surcharges. A 2026 conversion affects 2028 Medicare premiums. If the conversion pushes your MAGI above the first IRMAA tier ($109,000 single / $218,000 joint in 2026), you could pay an extra $81.20 to $487.00 per month in Medicare surcharges.
When is a Roth IRA conversion worth the upfront tax cost?
A Roth conversion is typically worth it when: (1) You expect to be in a higher tax bracket in future years than you are today; (2) You want to reduce or eliminate future RMDs that begin at age 73 or 75; (3) You have cash outside the IRA to pay the conversion tax bill without touching the converted funds; or (4) You want to leave tax-free inherited accounts to beneficiaries who would otherwise owe income tax on inherited Traditional IRA distributions.
Can I pay the Roth conversion tax bill out of the IRA funds being converted?
While technically possible, paying conversion taxes from the IRA itself is a significant mistake. If you are under age 59½, funds withheld for taxes trigger a 10% early withdrawal penalty on that withheld amount. Even if over 59½, using IRA funds to pay taxes reduces the amount that enters tax-free growth. Always pay the conversion tax using funds from a taxable account such as a savings or checking account.
Is there an annual income limit or dollar cap on Roth IRA conversions?
No. Federal tax law places no income limit and no dollar cap on Roth IRA conversions. Unlike regular annual Roth IRA contributions — which are limited to $7,000 to $8,000 per year and phase out at higher incomes — you can convert any amount from a Traditional IRA regardless of your income level or how much you have already contributed this year.
What is the 5-year rule for converted Roth IRA funds?
Each converted amount has its own 5-year clock. If you withdraw converted principal within 5 years of conversion AND you are under age 59½, you may owe a 10% early withdrawal penalty on those converted funds (not on earnings — that is a separate rule). Once you reach age 59½, converted principal can be withdrawn penalty-free at any time regardless of the 5-year clock.
What is "bracket filling" and how does it reduce my lifetime tax bill?
Bracket filling is the strategy of converting just enough each year to "fill up" your current lower tax bracket without crossing into a higher one. For example, if your 2026 taxable income is $30,000 and the top of the 22% bracket is $103,350 (single), you could convert up to $73,350 additional dollars all taxed at 22% — avoiding the 24% bracket and keeping future RMDs lower. Done over multiple years, this systematically moves money into a Roth at the lowest possible tax rates.
How do I avoid triggering an IRMAA surcharge when doing a Roth conversion?
The key is to check the current-year IRMAA thresholds and plan your conversion amount so your total MAGI stays below the first tier. For 2026, the base IRMAA threshold is $109,000 (single) or $218,000 (joint). Leave a $2,000 to $3,000 buffer below the threshold to account for estimation errors. Use our Medicare IRMAA Calculator to see exactly which tier your post-conversion MAGI lands in before committing to a conversion amount.
Other Free Retirement Planning Tools You May Find Useful
For full guidance on retirement tax planning, visit our IRS & Retirement Tax education hub. Before executing a Roth conversion, understand how your future Required Minimum Distributions will look using our RMD Calculator by Age, and verify the Medicare cost impact using the IRMAA Surcharge Calculator. If you plan to take IRA withdrawals before converting, use the IRA & 401(k) Withdrawal Planner to model your annual drawdown and net tax impact. Explore the Medicare costs and coverage hub to understand how IRMAA surcharges affect your total Medicare bill.
About This Educational Estimate: This tool is for educational purposes only. Seniors Audit uses the official formulas published by Internal Revenue Service (IRS), but results are estimates based on the information you entered. Rules, rates, and eligibility thresholds change annually and vary by individual circumstance.
Always verify your specific result directly with Internal Revenue Service (IRS) at 1-800-829-1040 or at www.irs.gov/retirement-plans/roth-comparison-chart before making enrollment, coverage, or financial decisions.
If you have Medicare questions, a free SHIP counselor in your state can review your specific situation at no cost — find yours at shiphelp.org.
Seniors Audit is independent and not affiliated with any government agency or insurance company. We are not affiliated with, endorsed by, or connected to any government agency, insurance company, or financial services firm. All calculations use the official formulas and current figures published by the agencies listed above. We do not receive payment for referrals, leads, or any action taken by visitors to this site. Last reviewed: July 2026.