Income after deductions, before the conversion
Traditional IRA/401(k) moved to Roth
Disclaimer
This tool provides estimates for educational purposes only and is not tax or investment advice. It models 2026 federal income tax on the converted amount and ignores state tax, IRMAA, NIIT, the pro-rata rule, and your full situation. Consult a qualified tax professional before converting.
How this is calculated
A Roth conversion is taxed as ordinary income in the year of the conversion. We stack the converted amount on top of your current taxable income and take the difference in federal tax:
- Tax on conversion = federal tax on (current income + conversion) − federal tax on current income alone.
- Effective rate = tax on conversion ÷ conversion amount.
- Room to top of bracket = the next 2026 bracket threshold minus your current taxable income.
- Amounts above that room are taxed at the next, higher marginal rate.
Uses the official 2026 ordinary income tax brackets (IRS Revenue Procedure 2025-32). It estimates federal income tax only; IRMAA, NIIT, the IRA aggregation (pro-rata) rule, and state tax are not modeled.
Sources
- IRS — Revenue Procedure 2025-32 (2026 inflation adjustments)
- IRS — Rollovers and Roth Conversions FAQ
Reviewed against 2026 figures · Last updated June 5, 2026
What is Roth Conversion Tax Calculator?
A Roth conversion calculator estimates the federal income tax you would owe when moving money from a Traditional IRA or 401(k) into a Roth account. The converted amount is added to your taxable income for the year, so it is taxed at your marginal rate and above. This tool uses the official 2026 tax brackets to show the tax on a conversion, the effective rate, and how much you can convert while staying inside your current bracket — the popular 'fill-the-bracket' strategy.
How to Use
- Enter your current taxable income for the year, before the conversion.
- Choose your filing status.
- Enter the amount you plan to convert from Traditional to Roth.
- Review the federal tax, effective rate, and your marginal rate before and after.
- Use the "room to top of current bracket" figure to size a fill-the-bracket conversion.
Why Use This Tool?
Tips & Best Practices
- Convert in low-income years (early retirement, gap years, market dips)
- Fill your current bracket rather than spilling into the next one
- Pay the conversion tax from outside cash, not the IRA, when possible
- Watch IRMAA: higher income can raise Medicare premiums about two years later
- Large conversions can trigger the 3.8% NIIT and tax more Social Security
- Spread conversions over several years to stay in lower brackets
Frequently Asked Questions
How is tax on a Roth conversion calculated?
The converted amount is added to your ordinary taxable income. The tax is the difference between your total tax with and without the conversion, so the dollars are taxed at your marginal rate and above. Large conversions can push part of the amount into higher 2026 brackets.
What is a fill-the-bracket Roth conversion strategy?
Convert just enough to reach the top of your current bracket without entering the next one. For 2026, a single filer with $60,000 taxable income (22% bracket up to $105,700) could convert about $45,700 and stay in the 22% bracket. This calculator shows that headroom.
What are the 2026 federal tax brackets?
Single 2026: 10% to $12,400; 12% to $50,400; 22% to $105,700; 24% to $201,775; 32% to $256,225; 35% to $640,600; 37% above. Married filing jointly brackets are roughly double. Source: IRS Revenue Procedure 2025-32.
Does a Roth conversion affect Medicare premiums (IRMAA) or NIIT?
It can. A conversion raises your modified adjusted gross income, which may increase Medicare Part B and D premiums (IRMAA) about two years later and can affect the 3.8% Net Investment Income Tax and how much Social Security is taxed. This tool estimates federal income tax only.
When does a Roth conversion make sense?
Often in lower-income years — early retirement before Social Security and RMDs, a gap year, or a market dip — when your marginal rate is temporarily low. The idea is to pay tax now at a lower rate than you would later on withdrawals or required minimum distributions.
Should I pay the conversion tax from the IRA or from cash?
Paying from outside cash is usually better, since it lets the full converted amount keep growing tax-free. Paying from the IRA reduces the amount converted and, if you are under 59½, the withheld portion can be a taxable distribution subject to a 10% penalty.
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