What this calculator does
Find out what it costs to move money from a traditional IRA to a Roth, and whether it's likely to pay off. You pay income tax on the amount now. In return, the money can grow and come out tax-free later.
Enter your income, the amount to convert and the tax rate you expect later. The calculator uses the 2026 federal brackets to find the tax, and shows which brackets the conversion lands in. It then compares converting with staying traditional, and finds the break-even.
Where it's used
Why this math matters outside the classroom:
- Filling a bracket. A single filer with $40,000 of taxable income has $10,400 of room before the 12% bracket ends at $50,400.
- Crossing a bracket. That same filer converting $20,000 pays $1,248 at 12% and $2,112 at 22%, or $3,360 in all.
- Comparing rates. A saver converting $10,000 at 22% pays $2,200 now, against $2,400 if the same money is taxed at 24% later.
- Growth over time. An account growing 6% a year multiplies by about 2.3966 over 15 years, so $50,000 becomes about $119,828.
How to use it
- Choose your filing status, and enter your taxable income before converting.
- Enter the amount to convert and your state tax rate.
- Enter the tax rate you expect later, the number of years and a yearly return.
- Choose how you'd pay the tax, then read the cost and the break-even.
What the inputs mean
- Taxable income before converting
- Use taxable income, which is your income after deductions. The conversion stacks on top of it, so this decides which brackets it lands in.
- Amount to convert
- The pre-tax amount moving from a traditional IRA to a Roth IRA.
- State tax rate on the conversion (optional)
- Enter your top state income tax rate. Some states don't tax this income, and some treat retirees differently. Use 0 if you'd pay no state tax.
- Tax rate on withdrawals later
- This is your best guess at the combined federal and state rate when you'd take the money out. It's the most important number here, so try a few.
- How would you pay the tax?
- Paying the tax from other savings usually works better, because the whole amount keeps growing tax-free. If you're under 59½ and hold back money from the conversion to pay the tax, that money can face a 10% early-withdrawal tax.
- Tax rate on those savings' yearly earnings
- If you stay traditional, the money you'd have paid in tax stays in a regular account. That account's earnings get taxed each year, which slows its growth.
Formula and method
federal tax = tax on (income + conversion) − tax on income tax now = federal tax + conversion × state rate your conversion rate = tax now ÷ conversion tax from other savings: break-even later rate = tax now × A ÷ (conversion × G) tax from the conversion: break-even later rate = tax now ÷ conversion
A conversion adds to your income for the year. It stacks on top of your other income, so a large one can reach higher brackets. Your rate on the conversion is usually higher than your overall rate.
The break-even later rate is the key result. G is how much the account grows over the years, and A is how much a regular taxable account grows. If your later rate would be above the break-even, converting comes out ahead.
If the tax comes out of the conversion, it's a straight rate comparison. The number of years doesn't matter. If the tax comes from other savings, time helps, because Roth growth is tax-free and the regular account's growth isn't.
Worked example
You file jointly with $120,000 of taxable income. You convert $50,000. Your state rate is 5%, and you expect a 24% rate later. You'd pay the tax from savings, with 6% growth over 15 years, and a 15% tax on those savings' earnings.
- Federal tax rises from $15,824 to $26,824, so the conversion costs $11,000.
- State tax: $50,000 × 5% = $2,500.
- Tax now: $11,000 + $2,500 = $13,500, which is 27% of the conversion.
- Convert: $50,000 grows to $119,827.91, tax-free.
- Stay: $119,827.91 × 76%, plus $13,500 × 2.1088 in savings, comes to $119,538.36.
- Converting is ahead by $289.55. The break-even later rate is 23.76%.
Result: The conversion costs $13,500 now and pays off after 14 years, if your later rate is 24%.
Understanding the result
If your later rate is above the break-even, converting wins over this period. If it's below, staying traditional wins. A close result like the example means the tax rates alone don't settle it.
A conversion can have side effects that this comparison leaves out. It raises your income for the year, which can raise your Medicare premiums through IRMAA two years later. It can also make more of your Social Security taxable.
Many people convert smaller amounts over several years, filling up a low bracket each time. Use the bracket table to see how much room you have.
Assumptions and limitations
- The whole conversion is pre-tax money, and it's taxed as ordinary income in 2026.
- Both accounts earn the same steady return.
- Your later rate applies to the whole traditional balance as one flat rate.
- The savings' earnings are taxed every year at the rate you enter.
- It doesn't include IRMAA, the tax on Social Security, required minimum distributions, or lost credits and deductions. Use the linked calculators to check IRMAA and Social Security.
- If you have after-tax money in any traditional IRA, part of your conversion isn't taxed. IRS rules set the taxable share, and that isn't modeled.
- Each conversion has its own five-year clock for early withdrawals. You also can't undo a conversion once it's made.
- This is an estimate for planning, not tax advice. Check your numbers with a tax professional before converting.
Frequently asked questions
How much tax will I pay on a Roth conversion?
The pre-tax amount you convert counts as income for the year, taxed at your federal and state rates. It stacks on top of your other income, so large conversions can reach higher brackets.
What is the break-even on a Roth conversion?
It's the later tax rate where converting and staying traditional come out equal. If you expect a higher rate later, converting wins.
Can a Roth conversion raise my Medicare premiums?
Yes. It adds to your income, and Medicare looks at your tax return from two years earlier. A large conversion can push you into an IRMAA surcharge tier.
Does a Roth conversion affect Social Security?
It can. The conversion counts in the income test, so more of your benefits may become taxable that year.
Can I reverse a Roth conversion?
No. Conversions made in 2018 or later can't be undone, so be sure of the amount first.
Sources
- IRS Publication 590-A, Contributions to Individual Retirement Arrangements (checked 2026-10-31)
- IRS Publication 590-B, Distributions from Individual Retirement Arrangements (checked 2026-10-31)
- IRS, Rev. Proc. 2025-32, tax year 2026 adjustments (checked 2026-10-31)
How this calculator is checked
Method: Federal tax from the 2026 bracket tables in src/lib/finance/tax-2026.ts (Rev. Proc. 2025-32). Conversion income and no-recharacterization rules read from Publication 590-A (2025), and the five-year rule from Publication 590-B (2025). The break-even math is derived from the two after-tax values; tests use hand-worked cases. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-31. Found a problem? Tell us.
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