A Roth conversion calculator shows the income tax due when you move money from a traditional IRA to a Roth IRA, and what each choice is worth later. Formula: Tax now = amount × current rate; Roth later = amount × (1 + return)^years; traditional later = that same value × (1 − later rate). Converting $30,000 at a 22% rate costs $6,600 of tax this year. At a 6% return for 15 years, the Roth grows to $71,896.75, while the traditional IRA nets $56,079.46 after tax at 22%.
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How to use the Roth conversion calculator
- Enter the amount you plan to convert.
- Enter the tax rate that will apply to the converted amount this year.
- Enter the tax rate you expect when you would withdraw the money instead.
- Enter the expected yearly return and the years until withdrawal.
The Roth conversion calculator shows the tax due now, the Roth balance if you pay the tax from other money, the traditional IRA value after tax, and the difference.
What formula does the Roth conversion calculator use?
- Tax due now = amount converted × current rate.
- Roth balance later = amount × (1 + return) raised to the years.
- Traditional balance after tax = the same grown value × (1 − later rate).
- Difference = Roth balance − traditional balance after tax.
Roth conversion calculator worked example
A $30,000 conversion over 15 years at 6% with a 22% rate this year:
| Later tax rate | Tax now | Roth later | Traditional after tax | Difference |
|---|---|---|---|---|
| 12% | $6,600 | $71,896.75 | $63,269.14 | $8,627.61 |
| 22% | $6,600 | $71,896.75 | $56,079.46 | $15,817.28 |
| 32% | $6,600 | $71,896.75 | $48,889.79 | $23,006.96 |
Converting at 12% instead of 22% would cut the tax now to $3,600.
How to read the difference
The Roth column assumes you pay the $6,600 from money outside the IRA. That money would also have grown if you had kept it. At 6% for 15 years, $6,600 becomes $15,817.28, the same as the difference when the two tax rates are equal. In other words, if your rate is the same now and later, a conversion is close to break-even before other factors.
So the real question the Roth conversion calculator helps answer is whether your rate later will be higher or lower than today. If you expect a higher rate later, the conversion wins. If you expect a lower one, leaving the money in the traditional IRA often does.
Rules to know before converting
The IRS treats the taxable part of a conversion as income for the year. It is not subject to the 10% early-distribution tax when you convert, but IRS Publication 590-B explains that each conversion starts its own five-year period: if you take the converted amount out within five years and are under 59½, the 10% additional tax can apply. Conversions cannot be undone; recharacterizing a conversion is no longer allowed.
If you have both pre-tax and after-tax money in traditional IRAs, the pro-rata rule decides how much of the conversion is taxable. The Roth conversion calculator treats the whole amount as taxable, so adjust the amount if part of it is basis.
Side effects on other bills
A conversion raises adjusted gross income, which can push other figures over a line. Two years later it can trigger a Medicare IRMAA surcharge; this year it can raise the taxable share of Social Security, reduce credits, or change the premium tax credit. Splitting a large conversion across several years often keeps you in a lower bracket. Use the Roth conversion calculator one year at a time, with the rate that applies to the top slice of income.
Required minimum distributions cannot be converted. If you are already taking them, take the year’s RMD first and convert only amounts above it.
Estimates for education only, not tax, legal or financial advice. Check current rules with the tax authority or a qualified adviser.
Related converters and calculators
Related calculators:
- Roth IRA calculator: growth
- IRA calculator: traditional IRA
- RMD calculator: required distributions
Sources
IRS Publication 590-B: Distributions from IRAs; IRS: Roth IRAs; IRS Publication 590-A: Contributions to IRAs.
Questions about this calculator
How is a Roth conversion taxed?
The taxable part is added to your income for the year and taxed at your ordinary rates.
Is there a penalty for converting?
No 10% tax applies to the conversion itself, but withdrawing converted money within five years before age 59½ can trigger it.
Can I undo a Roth conversion?
No. Recharacterizing a conversion is no longer allowed.
Should I pay the tax from the IRA?
Paying it from other money keeps more in the Roth. If you are under 59½, tax withheld from the IRA can also be subject to the 10% additional tax.
When does a Roth conversion make sense?
Usually when you expect a higher tax rate later than the rate on the conversion today.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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