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United States

Roth Conversion Tax Calculator

Legal basis: IRC §408A (Roth IRAs) · checked 2026-10-04 · Rates and limits change — verify the current figures.

A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA, and under IRC Section 408A the converted amount is included in your gross income as ordinary income in the year of the conversion. You pay the tax now, from money outside the account if possible; in exchange, the converted balance grows tax-free and qualified withdrawals in retirement are never taxed again. Roth IRAs also have no lifetime required minimum distributions, which makes conversions a standard tool for managing taxable income in retirement.

The tax is not a flat percentage. A conversion is stacked on top of your other taxable income and fills your tax brackets from the bottom up, so the first converted dollars may be taxed at 10 or 12 percent while later dollars spill into the 22 or 24 percent bracket. The right way to measure the cost is incremental: compute the tax on your income without the conversion, compute it again with the conversion added, and take the difference. That difference, divided by the conversion amount, is the blended rate you are actually paying.

The size of the conversion should be chosen with the bracket map in front of you. Many retirees convert exactly enough each year to fill a low bracket without crossing into the next one, spreading a large pre-tax balance over several years. Two complications matter. The five-year rule means each conversion starts its own five-year clock before earnings can be withdrawn tax-free, though converted principal comes out first and penalty-free after age 59½. And if you hold both deductible and non-deductible traditional IRA money, the pro-rata rule forces every conversion to carry a proportional share of your pre-tax balance, which is why the simple backdoor Roth move breaks when a large rollover IRA exists.

This calculator models a three-bracket progressive structure with editable thresholds and rates, so you can shape it to your own situation - including using the top rate field for the 24, 32, 35, or 37 percent bracket at higher incomes. The defaults are illustrative single-filer widths; verify the current-year bracket amounts, which are inflation-indexed, and confirm the strategy with a CPA or fiduciary adviser.

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Calculate

$
The balance moved from a traditional IRA or 401(k) to a Roth IRA this year.
$
Taxable income from all other sources, after the standard or itemized deduction.
$
Taxable income where the second rate begins. 2025 single figure shown; roughly double for married filing jointly - verify current-year amounts.
$
Taxable income where the third rate begins. 2025 single figure shown; roughly double for married filing jointly - verify current-year amounts.
%
%
%
Enter your marginal rate - 22, 24, 32, 35 or 37 percent - for the income band your conversion reaches.
Additional tax on the conversionordinary income tax, due with the year's return$8,800
Blended rate on the conversionacross every bracket the conversion touches22.0%
Top marginal rate reachedthe rate on your last converted dollar22%
Federal tax before the conversion$5,914
Federal tax after the conversion$14,714
Amount landing in the Rothwhen the tax is paid from funds outside the account$40,000
Roth amount if tax comes from proceedspaying tax from the converted amount reduces what compounds tax-free$31,200
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How the math works

  • Taxable income after conversion = taxable income before + the converted amount.
  • Tax(x) = rate1 × the portion of x in the first bracket + rate2 × the portion in the second + rate3 × everything above the second threshold.
  • Incremental tax = Tax(income + conversion) − Tax(income); blended rate = incremental tax ÷ conversion.
  • Bracket thresholds and rates are inflation-indexed inputs; verify current-year amounts with the IRS.

Frequently asked questions

How is a Roth conversion taxed?
The converted amount is added to your ordinary income for the year and taxed at your regular brackets - there is no separate conversion rate and, for a conversion from a pre-tax account, no early-withdrawal penalty on the converted principal. Because the conversion stacks on top of other income, the incremental tax depends on which brackets it fills.
What is the pro-rata rule?
If you hold any non-deductible (after-tax) money in traditional IRAs, each conversion must take a proportional share of pre-tax and after-tax money across all your traditional, SEP and SIMPLE IRAs. You cannot cherry-pick the after-tax dollars, which is why a large rollover IRA from an old 401(k) can make a backdoor Roth mostly taxable. IRS Form 8606 tracks the after-tax basis.
What are the five-year rules?
Converted principal can be withdrawn penalty-free after age 59½, but each conversion starts its own five-year clock if you are younger, with a 10 percent penalty on early withdrawal of converted amounts. Separately, earnings in any Roth account become tax-free only after the account has been open five years and you are 59½, disabled, or another exception applies.
How much should I convert in a year?
A common approach is to convert up to the top of your current bracket without crossing into the next one, repeating across several low-income years such as the gap between retirement and required minimum distributions. Because the conversion raises adjusted gross income, also watch its effect on Medicare IRMAA surcharges two years later.
Should I pay the conversion tax from the converted account?
Paying from outside funds is generally better: the full amount stays in the Roth and compounds tax-free, and if you are under 59½ the portion withheld for taxes is treated as a distribution and can trigger a 10 percent penalty. The calculator shows both outcomes so you can see the difference.
Does a conversion affect my Medicare premiums?
Yes. The conversion increases your modified adjusted gross income, and IRMAA surcharges on Medicare Part B and Part D are set by your MAGI from two years earlier. A large conversion in one year can raise your premiums two years running, which is another argument for spreading conversions across several years.
Can I undo a conversion?
Recharacterizations of Roth conversions were eliminated for tax years 2018 and later, so a conversion is effectively permanent. You can still withdraw converted money later, but the tax bill for the conversion year stands. Decide the amount carefully before December 31.

This calculator is an educational estimate, not tax or financial advice. Bracket thresholds and rates are inflation-indexed and change annually, and the three-bracket model here is a simplification of the full schedule. Verify current-year figures with the IRS and confirm your conversion strategy with a CPA or fiduciary adviser.

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