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Roth Conversion Calculator: Tax and IRMAA Impact

See what a Roth conversion really costs: the extra federal income tax, how much you can convert before reaching the next bracket, the senior deduction you could lose, and whether the conversion pushes your Medicare premiums into an IRMAA bracket two years later.

Updated By Hassan Arslan How we build & check our calculators

Your income and conversion

Your expected adjusted gross income for the year without the conversion: pensions, IRA withdrawals, wages, the taxable part of Social Security and so on.

Leave 0 to use the standard deduction.

Pre-tax money moving from a traditional IRA or 401(k) to a Roth.

Interest, dividends, capital gains and rental income included in your income above. Used for the 3.8% net investment income tax.

Used to estimate IRMAA, which looks back two years.

Your results

Extra federal income tax

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Room left in your bracket

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Senior deduction lost

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IRMAA two years later

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What the conversion costs

How much you can convert before each bracket

Estimate for education only, based on your inputs and the rules explained below. Not financial, tax or legal advice. How we calculate

How to use this calculator

  1. Choose the tax year and filing status.
  2. Enter your income before the conversion: your expected adjusted gross income for the year, including the taxable part of any Social Security benefits.
  3. Enter itemized deductions if you itemize, and how many people on the return are 65 or older. That sets your standard deduction and the senior deduction.
  4. Enter the amount you’re thinking of converting and how many people in your household will be on Medicare in two years.
  5. Read the bracket table to find the largest conversion that stays in your current bracket, or the next one.

How a Roth conversion is taxed

Converting pre-tax money from a traditional IRA or 401(k) to a Roth account adds the converted amount to your income for the year. It’s taxed as ordinary income, at your marginal rates, but it isn’t subject to the 10% early withdrawal penalty. In exchange, qualified withdrawals from the Roth later are tax-free, and Roth IRAs have no required minimum distributions during your lifetime.

Because each bracket taxes only the income inside it, many people “fill up” a bracket: they convert just enough to reach the top of the 12%, 22% or 24% bracket and stop there. The table in the calculator shows those amounts for your situation. See all the thresholds on our 2026 tax brackets page.

The costs beyond your tax bracket

A conversion raises your adjusted gross income, and several other things depend on that number:

  • Medicare IRMAA: premiums two years later rise if your MAGI crosses a threshold, even by $1. In 2026, the first threshold is $109,000 for individuals and $218,000 for joint filers. See the 2026 IRMAA brackets.
  • The senior deduction: for 2025 through 2028, the $6,000 deduction for people 65 and older shrinks by 6% of MAGI over $75,000 ($150,000 joint), so a conversion in that range is taxed at a higher effective rate.
  • Social Security taxes: more income can make more of your Social Security benefits taxable. This calculator doesn’t include that effect, so if you receive benefits and your income is modest, your real cost may be higher. The Social Security tax calculator shows what each extra $1,000 of income costs.
  • ACA subsidies: if you buy Marketplace coverage before Medicare, a conversion can push you over the 400% subsidy cliff. Check the 2026 ACA income limits.
  • Net investment income tax: the 3.8% tax applies to investment income once MAGI is over $200,000 ($250,000 joint, $125,000 married filing separately). A conversion isn’t investment income itself, but it raises MAGI, so it can pull your dividends, interest and gains into the tax. Enter your investment income above to include it.

Worked examples

  • Married, both 65, $90,000 of other income, converting $50,000 in 2026: the whole conversion stays in the 12% bracket, so it adds $6,000 of federal tax. They could convert up to $58,300 before reaching the 22% bracket, and stay under IRMAA.
  • Single, 65, $70,000 of other income, converting $30,000: the conversion pushes income into the 22% bracket and cuts the senior deduction by $1,500. Total extra tax: $6,475, or 21.6% of the conversion.
  • Single, $100,000 of other income, converting $15,000: MAGI of $115,000 crosses the first IRMAA threshold, adding about $1,148 to Medicare premiums two years later at 2026 rates. Converting $9,000 instead would avoid it.

When a conversion can make sense

  • Low-income years, such as between retirement and the start of Social Security or required minimum distributions, when you’re in a lower bracket than you expect to be later.
  • Before required minimum distributions start, to shrink the traditional balance that RMDs will force you to withdraw.
  • When you can pay the tax from savings outside the IRA, so the full amount keeps growing in the Roth.
  • For heirs: a Roth can pass to beneficiaries without the income tax that inherited traditional IRA withdrawals carry.

It usually makes less sense if you’ll need the money within five years, expect a lower tax rate in retirement, or would have to pay the tax from the converted money itself. Converted amounts withdrawn within five years may owe the 10% penalty if you’re under 59½.

How the calculator works

Taxable income = AGI − larger of (standard deduction, itemized) − senior deduction Extra tax = federal tax with the conversion − federal tax without it IRMAA estimate = surcharge at (AGI + conversion) − surcharge at AGI, using 2026 brackets

We use the 2025 or 2026 federal brackets, standard deduction and senior deduction phase-out. MAGI for IRMAA is taken as your AGI (add any tax-exempt interest to your income if you have it).

The IRMAA brackets for the year a conversion affects aren’t published yet, so we use the latest ones; future thresholds usually rise with inflation. The estimate excludes capital gains rates, the taxable part of Social Security, credits and state taxes. It isn’t tax advice.

Frequently asked questions

How much tax will I pay on a Roth conversion?
The converted amount is added to your taxable income for the year and taxed at your ordinary income tax rates. If it all fits in the 12% bracket, you pay about 12% of the conversion; if it pushes you into the 22% or 24% bracket, the part above the threshold is taxed at the higher rate. Pre-tax money only: any after-tax contributions (basis) in the account aren’t taxed again.
Can I undo a Roth conversion?
No. Since 2018, a conversion can’t be recharacterized back to a traditional IRA. Run the numbers before you convert, and consider converting late in the year, when you know your income better.
Does a Roth conversion affect my Medicare premiums?
It can. A conversion raises your modified AGI, and Medicare’s IRMAA surcharges use your income from two years earlier, so a 2026 conversion can raise your 2028 Part B and Part D premiums. In 2026, IRMAA starts above $109,000 of MAGI for individuals and $218,000 for joint filers.
What is the deadline for a Roth conversion?
A conversion counts for the calendar year in which the money leaves the traditional account, so it must be completed by December 31. Unlike IRA contributions, you can’t make a conversion for last year after the year ends.
Should I pay the tax from the conversion itself?
Paying the tax with money from outside the IRA leaves more in the Roth to grow tax-free. If you’re under 59½ and have tax withheld from the conversion, the withheld amount counts as a distribution that may owe the 10% early withdrawal penalty.

Sources

Key terms

About this calculator. Calcvera’s Roth Conversion Calculator: Tax and IRMAA Impact is written and maintained by Hassan Arslan and was last reviewed on September 29, 2026. Rules and figures are checked against “Publication 590-A, Contributions to Individual Retirement Arrangements (conversions)”, “Roth IRAs” and the other sources listed above. Results are estimates for education — not financial, tax or legal advice. Found an error? Tell us and we'll fix it. See our methodology and editorial policy.