Free calculator
Roth Conversion Tax Calculator
What a conversion actually costs, the correct blended rate, not marginal × amount.
Reviewed September 2, 2026
Short answer
A conversion is taxed at the blended (span-integrated) rate across the brackets it fills, not your top marginal rate times the amount. Converting $30,000 on $80,000 of single income in 2026 costs $6,600, a flat 22%.
- Taxed at 22%$30,000.00
- Remaining room in bracket$11,800.00
This conversion adds approximately $6,600.00 of federal income tax, an effective rate of 22.0% across the converted amount. It does not include state tax or income-related benefit and premium changes.
2026 federal brackets and standard deduction (IRS Rev. Proc. 2025-32, post-OBBBA). Single and married-filing-jointly are modeled; head of household and married-filing-separately are not. Federal income tax only, state tax, IRMAA, NIIT, and the effect on Social Security taxation are not included. The cost shown is the span-integrated effective rate over the converted amount, so a conversion that crosses a bracket is taxed partly at each rate.
This is an educational estimate, not tax or financial advice. Figures reflect the law year shown and the inputs you provide. Consult a qualified professional before acting.
Sources
- Revenue Procedure 2025-32 — Internal Revenue Service
The 2026 federal income-tax brackets and standard deductions.
Accessed September 2, 2026
- Roth IRAs — Internal Revenue Service
Roth IRA contribution, distribution, and conversion tax treatment.
Accessed September 2, 2026
How it’s calculated
- Start from your other 2026 taxable income after the standard deduction, which sets the bracket the conversion stacks on top of.
- Add the conversion above it; each dollar is taxed at the bracket it lands in, so a conversion crossing a bracket is taxed partly at each rate.
- Sum the tax across that span and divide by the amount converted for the true effective rate, not marginal × amount.
Worked Roth conversion example
- Other ordinary income
- $80,000
- Conversion
- $30,000
- Filing status
- Single
- Tax year
- 2026
Result
$6,600 of additional federal income tax, a 22% effective rate.
After the standard deduction, this example's conversion remains inside the 22% bracket. A conversion that spans brackets would be split across those rates instead.
What this calculator does not cover
- State income tax, NIIT, credits, and deductions other than the standard deduction are not modeled.
- The result does not price IRMAA, ACA premium-tax-credit changes, or additional Social Security taxation.
- Only single and married-filing-jointly statuses are supported.
Frequently asked
- Why isn't it just my tax bracket times the amount?
- Because a large conversion can climb through several brackets. The correct cost integrates the rate across the whole span you convert; your top marginal rate overstates it, and your current bracket alone understates it.
- What does this calculator leave out?
- Federal income tax only, single or married-filing-jointly. It does not model state tax, Medicare IRMAA, NIIT, or how the added income changes Social Security taxation. A full Meridary plan sequences the flat state rate and the Social Security effect together with the conversion; IRMAA and the ACA cliff stay in these free calculators rather than the projection engine, and NIIT is out of scope.