Roth IRA Conversion Calculator — Tax Impact Analysis
Tax Cost of Conversion
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Roth Future Value (tax-free)
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Traditional Future Value (after tax)
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Net Benefit of Converting
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How a Roth Conversion Works
A Roth IRA conversion is the process of moving money from a Traditional IRA (pre-tax retirement account) to a Roth IRA (after-tax retirement account). You pay ordinary income tax on the converted amount in the year of conversion, but all future growth and qualified withdrawals from the Roth are completely tax-free. According to the Internal Revenue Service (IRS), there is no income limit or cap on how much you can convert in a single year, making Roth conversions available to all taxpayers regardless of income level. The key decision hinges on whether paying taxes now at your current rate produces a better long-term outcome than paying taxes later at your expected future rate.
According to the Investment Company Institute, Americans held approximately $13.6 trillion in IRAs as of 2024, with Traditional IRAs holding roughly $11.8 trillion and Roth IRAs about $1.8 trillion. The growing popularity of Roth conversions reflects concerns about future tax rate increases and the desire to eliminate Required Minimum Distributions (RMDs). Unlike Traditional IRAs, Roth IRAs have no RMDs during the owner's lifetime, allowing assets to grow tax-free indefinitely. This calculator compares the after-tax future value of keeping your money in a Traditional IRA versus converting to Roth, accounting for the upfront tax cost, expected growth rate, and time horizon.
How the Roth Conversion Tax Impact Is Calculated
The core calculation compares two scenarios. Scenario A (Convert): Pay tax on the conversion amount now at your current marginal rate. The remaining amount grows tax-free in the Roth. Roth Future Value = Conversion Amount x (1 + Return Rate)^Years. Scenario B (Keep Traditional): The full amount grows tax-deferred. At withdrawal, pay tax at your future rate. Traditional After-Tax Value = Conversion Amount x (1 + Return Rate)^Years x (1 - Future Tax Rate). The Net Benefit = Roth Future Value - Traditional After-Tax Value - Tax Cost of Conversion.
Worked example: Convert $100,000 at a 24% current tax rate with a 28% expected future rate, 7% annual return, and 20 years to retirement. Tax cost now = $100,000 x 0.24 = $24,000. Roth future value = $100,000 x (1.07)^20 = $386,968 (all tax-free). Traditional future value after tax = $386,968 x (1 - 0.28) = $278,617. Net benefit of converting = $386,968 - $278,617 - $24,000 = $84,351. The conversion saves over $84,000 in this scenario. Use our 401(k) calculator to model your full retirement picture.
Key Terms You Should Know
- Traditional IRA -- A retirement account where contributions may be tax-deductible and grow tax-deferred. Withdrawals in retirement are taxed as ordinary income. Subject to Required Minimum Distributions starting at age 73 (as of 2024).
- Roth IRA -- A retirement account funded with after-tax dollars. Contributions and earnings grow tax-free, and qualified withdrawals (after age 59 1/2 and the 5-year rule) are completely tax-free. No RMDs during the owner's lifetime.
- Marginal tax rate -- The tax rate applied to the last dollar of your income. Conversion amounts are added to your ordinary income, so the marginal rate determines the tax cost of conversion.
- Required Minimum Distributions (RMDs) -- Mandatory annual withdrawals from Traditional IRAs starting at age 73. RMDs force you to take taxable distributions whether you need the money or not. Roth IRAs are exempt from RMDs.
- 5-year rule -- Roth conversion amounts must remain in the Roth for 5 years before they can be withdrawn penalty-free (if under age 59 1/2). This prevents people from using conversions to access retirement funds early.
- IRMAA (Income-Related Monthly Adjustment Amount) -- Higher Medicare Part B and D premiums triggered when modified adjusted gross income exceeds certain thresholds. Large Roth conversions can push you into IRMAA surcharge territory.
2025-2026 Federal Income Tax Brackets (Single Filers)
Understanding the current tax brackets is essential for planning how much to convert. Each dollar of Roth conversion is taxed at your marginal rate. Converting just enough to stay within a lower bracket ("bracket filling") is a common strategy.
| Tax Rate | 2025 Taxable Income (Single) | 2025 Taxable Income (Married Filing Jointly) |
|---|---|---|
| 10% | $0 - $11,925 | $0 - $23,850 |
| 12% | $11,926 - $48,475 | $23,851 - $96,950 |
| 22% | $48,476 - $103,350 | $96,951 - $206,700 |
| 24% | $103,351 - $197,300 | $206,701 - $394,600 |
| 32% | $197,301 - $250,525 | $394,601 - $501,050 |
| 35% | $250,526 - $626,350 | $501,051 - $751,600 |
| 37% | Over $626,350 | Over $751,600 |
Note: The Tax Cuts and Jobs Act (TCJA) provisions are scheduled to sunset after 2025, which could push rates back to pre-2018 levels (the 12% bracket would revert to 15%, the 22% bracket to 25%, etc.). This potential rate increase makes 2025 and early 2026 a strategic window for Roth conversions at relatively lower rates. Use the US income tax calculator to model different scenarios.
Practical Examples
Example 1 -- Early retiree gap years: A 55-year-old retiree has no earned income until Social Security starts at 67. Their only taxable income is a small pension of $20,000/year. With the standard deduction of $15,700, their taxable income is only $4,300 (10% bracket). They can convert approximately $44,175 of their Traditional IRA to Roth and stay entirely within the 12% bracket, paying only about $5,300 in conversion taxes on $44,175. Over 12 gap years, they could convert over $530,000 at the 10-12% rate.
Example 2 -- High earner bracket filling: A married couple earning $350,000 is in the 24% bracket. The 24% bracket extends to $394,600. They can convert up to $44,600 ($394,600 - $350,000) of Traditional IRA to Roth at the 24% rate, paying $10,704 in conversion taxes. If their future retirement tax rate is 32%, this saves $3,568 on just this year's conversion -- and the ongoing tax-free growth adds substantially more savings over decades.
Example 3 -- Down market conversion: During a market downturn, a $500,000 Traditional IRA has dropped to $350,000. Converting now means paying tax on $350,000 instead of $500,000 -- saving $36,000 in taxes at the 24% rate. When the market recovers, all the rebound growth occurs inside the Roth, completely tax-free. This strategy turns market declines into Roth conversion opportunities.
Tips and Strategies
- Use bracket filling: Convert just enough to fill your current tax bracket each year rather than doing one large conversion. This keeps you in lower brackets and spreads the tax burden over multiple years.
- Pay the conversion tax from outside the IRA: If possible, pay the tax bill from non-retirement funds. Using IRA money to pay conversion taxes reduces the amount that goes into the Roth and diminishes the long-term benefit.
- Watch for IRMAA cliffs: Large conversions can trigger Medicare premium surcharges that kick in at specific income thresholds. The first IRMAA threshold for 2025 is $106,000 (single) or $212,000 (married). Calculate the total cost including any IRMAA impact.
- Convert during low-income years: Sabbaticals, layoffs, early retirement, and years with large deductions create low-income windows where conversions are particularly tax-efficient. Use the retirement calculator to identify these opportunities in your timeline.
- Consider state taxes: This calculator focuses on federal tax rates. State income taxes (which range from 0% to 13.3% depending on your state) add to the conversion cost. Residents of no-income-tax states like Florida, Texas, and Nevada have an inherent advantage for Roth conversions.
Frequently Asked Questions
When does a Roth conversion make sense?
A Roth conversion makes the most financial sense when your current marginal tax rate is lower than the rate you expect to pay in retirement. Common situations include early retirement years before Social Security begins, years with unusually low income, years with large deductions, and the current pre-2026 tax environment where TCJA rates are still in effect. Conversions also make sense when you want to reduce future RMDs, pass tax-free assets to heirs, or build a diversified tax base between pre-tax and after-tax accounts for retirement flexibility.
Can I undo a Roth conversion?
No. Since the Tax Cuts and Jobs Act of 2018, the IRS eliminated the ability to recharacterize (undo) Roth conversions. Prior to 2018, you could reverse a conversion by the tax filing deadline if the investment lost value. This option no longer exists, making every Roth conversion a permanent, irrevocable decision. This means you should carefully model the tax impact before converting, especially for large amounts.
Do I have to convert all at once?
No, and in fact most financial advisors recommend against converting everything at once. Partial conversions allow you to spread the tax impact across multiple years, strategically filling up lower tax brackets each year without pushing yourself into a higher bracket. For example, if you have $500,000 in a Traditional IRA, converting $50,000-$80,000 per year over 7-10 years typically results in a lower total tax bill than converting the full amount in a single year.
How does a Roth conversion affect Medicare premiums?
Roth conversion income increases your Modified Adjusted Gross Income (MAGI), which can trigger Income-Related Monthly Adjustment Amounts (IRMAA) for Medicare Parts B and D. IRMAA surcharges are based on income from two years prior -- so a 2025 conversion affects your 2027 Medicare premiums. The first IRMAA threshold for 2025 is $106,000 for singles and $212,000 for married couples. Surcharges range from $70 to $408 per month per person. Factor this additional cost into your conversion analysis.
What is the 5-year rule for Roth conversions?
Each Roth conversion has its own 5-year clock. If you withdraw the converted amount (not earnings) before 5 years have passed and you are under age 59 1/2, you will owe a 10% early withdrawal penalty on the amount withdrawn. However, if you are already over 59 1/2, the 5-year rule does not apply to converted amounts -- only to earnings. The 5-year clock starts on January 1 of the year you make the conversion, so a December conversion and a January conversion in the same tax year have the same 5-year start date.
Should I convert during a market downturn?
Converting during a market downturn can be an excellent strategy because you pay tax on the reduced current value rather than the higher pre-decline value. When the market recovers, all of the rebound growth happens inside the Roth IRA, completely tax-free. For example, if a $500,000 IRA drops to $350,000, converting at the lower value saves $36,000 in federal taxes at the 24% rate. The key risk is that if the market declines further after conversion, you cannot undo it (no recharacterization since 2018), so you may have paid tax on a value that continued to fall.