Rex says
The sweet spot is the gap years — retired, not yet on Social Security, not yet taking RMDs. That's when you can convert into the low brackets on purpose.
Try a scenario
Click to load — tweak from there.Inputs
Result
Federal tax on the conversion
$7,505
Effective rate on converted dollars
12.51%
Marginal bracket after converting
22%
Room left in your current bracket
$56,950
Roth value at withdrawal
$154,310
After-tax value if you don't convert
$134,090
Conversion advantage
$20,220
Verdict
Converting wins at these assumptions
Converting comes out ahead by about $20,220. You have $56,950 of room before the next bracket — converting exactly to the top of your current bracket, every year, is the standard play.
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How to use this
- 1Enter amount to convert ($).
- 2Enter your other taxable income ($).
- 3Enter filing status.
- 4Enter expected tax rate in retirement (%).
- 5Enter assumed annual return (%).
- 6Enter years until you'd withdraw.
- 7Enter how will you pay the conversion tax?.
- 8Read your federal tax on the conversion on the right — it updates as you type.
- 9Hit Share to keep the scenario or send it to someone.
About this calculator
A Roth conversion moves money from a pre-tax IRA into a Roth, triggering ordinary income tax now in exchange for tax-free growth later. Whether it's a win comes down to two numbers: your rate today versus your rate when you'd otherwise withdraw. This calculator shows the tax bill, the bracket you'd land in, how much you could convert without crossing into the next bracket, and the year the conversion breaks even.
Worked example
Using the values the calculator loads with:
Inputs
- Amount to convert: 60000 $
- Your other taxable income: 70000 $
- Filing status: Married filing jointly
- Expected tax rate in retirement: 24 %
- Assumed annual return: 6.5 %
- Years until you'd withdraw: 15
- How will you pay the conversion tax?: From taxable savings (better)
Results
- Federal tax on the conversion: $7,505.00
- Effective rate on converted dollars: 12.51%
- Marginal bracket after converting: 22%
- Room left in your current bracket: $56,950.00
- Roth value at withdrawal: $154,310.46
- After-tax value if you don't convert: $134,090.34
- Conversion advantage: $20,220.12
- Verdict: Converting wins at these assumptions
What each field means
Inputs
- Amount to convert ($)
- The amount to convert used in the calculation, measured in $. Starts at 60000 $ so you have a working example on load.
- Your other taxable income ($)
- The your other taxable income used in the calculation, measured in $. Starts at 70000 $ so you have a working example on load.
- Filing status
- Pick the option that matches your situation — the maths changes per option. Choices: Single, Married filing jointly.
- Expected tax rate in retirement (%)
- The expected tax rate in retirement used in the calculation, measured in %. Starts at 24 % so you have a working example on load. Accepted range: 0–50 %.
- Assumed annual return (%)
- The assumed annual return used in the calculation, measured in %. Starts at 6.5 % so you have a working example on load. Accepted range: -10–20 %.
- Years until you'd withdraw
- The years until you'd withdraw used in the calculation. Starts at 15 so you have a working example on load. Accepted range: 1–50.
- How will you pay the conversion tax?
- Pick the option that matches your situation — the maths changes per option. Choices: From taxable savings (better), Withhold it from the conversion.
Results
- Federal tax on the conversion
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Effective rate on converted dollars
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Marginal bracket after converting
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Room left in your current bracket
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Roth value at withdrawal
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- After-tax value if you don't convert
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Conversion advantage
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Verdict
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
When does a Roth conversion make sense?
When your tax rate today is lower than the rate you expect when the money comes out. That's usually true in the gap years between retiring and starting Social Security or RMDs, in a year with unusually low income, or if you expect large RMDs to push you into a higher bracket later.
How is a Roth conversion taxed?
The converted amount is added to your ordinary income for the year. There is no early-withdrawal penalty on a conversion regardless of age, but each conversion carries its own five-year clock before the converted principal can be withdrawn penalty-free if you're under 59½.
Should I pay the conversion tax from the IRA itself?
Almost never, if you can avoid it. Withholding the tax from the conversion shrinks the amount that lands in the Roth and, under 59½, the withheld portion is treated as a taxable distribution with a penalty. Paying from taxable savings is materially better.
Does a Roth conversion affect Medicare premiums?
Yes. Conversion income counts toward modified adjusted gross income for IRMAA, which is assessed on a two-year lookback. A large conversion at 63 or later can raise Medicare Part B and D premiums, so many people convert in slices to stay under the brackets.
Is there a limit on how much I can convert?
No dollar limit and no income limit. You can convert any amount in any year. The practical limit is the tax bracket you're willing to fill — which is why converting to the top of a bracket, rather than all at once, is the common strategy.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
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Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Roth Conversion Calculator — Tax Cost and Break-Even (2026). Retrieved from https://www.revenuelab.fyi/toolbox/roth-conversion-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/roth-conversion-calculator" target="_blank" rel="noopener">Roth Conversion Calculator — Tax Cost and Break-Even (2026) — RevenueLab</a> (2026).</p>
Source: [Roth Conversion Calculator — Tax Cost and Break-Even (2026) — RevenueLab](https://www.revenuelab.fyi/toolbox/roth-conversion-calculator) (2026).