Roth Conversion Calculator
Enter figures from last year's tax return, adjusted for anything you expect to change this year, and a proposed traditional IRA to Roth conversion. See the added tax, how much you can convert while staying in each bracket, and the thresholds a conversion can trigger.
Return comparison
A 2026 projection with and without the conversion. Every line is recalculated, including Social Security taxation, the senior deduction, and deductions limited by income.
| Line | Without | With conversion | Change |
|---|---|---|---|
| Calculating… | |||
Where the conversion lands
Ordinary taxable income on the 2026 federal bracket scale. Qualified dividends and long-term gains are taxed separately on top of this amount.
How much you can convert by bracket
The largest conversion that keeps ordinary taxable income within each bracket, with all knock-on effects included.
| Stay within | Bracket top | Max conversion | Added tax | Avg rate |
|---|---|---|---|---|
| Calculating… | ||||
Thresholds to watch
Conversion amounts at which other rules start or stop applying. Medicare IRMAA premiums are set from income two years earlier, so a 2026 conversion affects 2028 premiums.
- Calculating…
Tax on each additional dollar converted
Federal plus state tax on the next dollar. Jumps above the bracket rate come from Social Security becoming taxable, the senior deduction phasing out, gains leaving the 0% rate, and the 3.8% investment income tax.
Assumptions
- Federal figures use the 2026 brackets, standard deduction, capital gain thresholds and SALT cap from IRS Rev. Proc. 2025-32 and the One Big Beautiful Bill Act, including the $6,000 senior deduction, the 0.5% charitable floor, the $1,000/$2,000 non-itemizer charitable deduction, and the 2/37 itemized limitation for the 37% bracket.
- Not modeled: AMT, 25%/28% capital gain rates, QBI wage and SSTB limits, credit phaseouts, and rules on later Roth withdrawals. Married filing separately assumes spouses lived together.
- Pro-rata rule: taxable conversion = conversion × (1 − basis ÷ (12/31 IRA value + conversion)).
- California tax uses the 2025 FTB rate schedules as an estimate until 2026 figures are published. Social Security is excluded and capital gains are taxed as ordinary income.
- IRMAA uses 2026 Medicare thresholds and surcharges per person as a proxy for 2028.
Planning a Roth conversion?
We'll build a full multi-year projection and help you choose the right amount and timing. Call (415) 431-9660 or (844) 356-9700.
This calculator provides estimates for planning purposes only and is not tax advice. Results depend on the accuracy of the figures entered and on assumptions that may not fit your situation. Consult TaxPlus & Associates before converting.