The formulas
- Added tax = tax(taxable income + conversion) - tax(taxable income)
- Effective rate = added tax / conversion
- Brackets: Rev. Proc. 2025-32 section 4.01
How it works
A Roth conversion adds the taxable part of the converted amount to ordinary income in the year of conversion. The 2026 brackets of 10% to 37% were made permanent by the One Big Beautiful Bill Act and indexed by Rev. Proc. 2025-32. The tool stacks the conversion on top of your other taxable income.
Use the backdoor Roth pro-rata calculator first if you hold after-tax basis in traditional IRAs; only the taxable part belongs here. The tool ignores capital gains rates, credits, the net investment income tax and state tax, and the extra AGI can change other income-based items.
Illustrative figures only. Check the result against your firm's methodology before relying on it.
Common questions
Is the 10% early withdrawal tax due on a conversion?
No, not on the conversion itself. A distribution of the converted amount within 5 years before age 59 1/2 can trigger it.
Can I undo a conversion?
No. Recharacterization of conversions ended for conversions after 2017.
Why convert only to the top of a bracket?
Filling the current bracket keeps the whole conversion at one marginal rate. The room-left row shows how much fits.
Sources
Runs in your browser. The figures you type are not sent to CORAA or stored. Check the result against your firm's methodology before relying on it.