Roth Conversion Tax Calculator
Estimate the 2026 tax cost of moving traditional IRA, SEP IRA, SIMPLE IRA, or employer-plan money into a Roth IRA. Model taxable basis, Form 8606 pro-rata treatment, federal bracket stacking, NIIT, optional state tax, withholding, RMD review, and Medicare premium flags.
Last Updated: May 31, 2026
Tax return before conversion
Start with 2026 AGI before the Roth conversion and the deduction assumption used to estimate taxable income.
Use adjusted gross income before adding the taxable part of the conversion.
The model keeps deductions fixed before and after the conversion.
Used only when itemized deduction mode is selected.
Used for early-distribution and Medicare planning warnings.
Used to flag potential low-tax conversion windows.
Conversion and basis
Estimate how much of the conversion is taxable. For IRA conversions with basis, the pro-rata rule looks across all traditional, SEP, and SIMPLE IRAs.
Use prior-year Form 8606 basis plus current-year nondeductible basis if applicable.
December 31 value after the conversion, used for Form 8606 pro-rata estimates.
Include other traditional, SEP, or SIMPLE IRA distributions in the same tax year.
Used only for employer-plan conversions with documented after-tax basis.
Tax add-ons and payment plan
Add NIIT, optional state tax, withholding, RMD, and Medicare premium review flags.
Use when net investment income may be exposed by higher MAGI.
Optional flat planning estimate. State Roth conversion treatment can vary.
Outside cash usually preserves more money inside the Roth IRA.
RMD amounts generally cannot be converted.
Use for Medicare IRMAA planning. This calculator flags but does not estimate IRMAA.
Conversion Tax Status
Low tax window
Taxable Conversion
$20,000.00
Regular Federal Tax Increase
$4,400.00
Total Estimated Tax
$4,400.00
Effective Conversion Rate
22%
Outside Cash Needed
$4,400.00
Income Stack
- AGI before conversion
- $90,000.00
- AGI after conversion
- $110,000.00
- Taxable income before
- $73,900.00
- Taxable income after
- $93,900.00
- Bracket room before
- $31,800.00
Basis And Pro-Rata
- Conversion source
- All pre-tax conversion estimate
- Nontaxable conversion
- $0.00
- Taxable percent
- 100%
- Pro-rata denominator
- $0.00
- Remaining IRA basis
- $0.00
Tax And Cash Flow
- Federal tax increase
- $4,400.00
- Additional NIIT
- $0.00
- State tax estimate
- $0.00
- Payments entered
- $0.00
- Roth amount preserved
- $20,000.00
Federal Bracket Impact
The estimated total conversion tax rate is below the future marginal rate entered, so this may be a tax-window year if the other return effects are acceptable.
| Bracket | Rate | Conversion taxed here | Additional federal tax |
|---|---|---|---|
| $50,400.00 to $105,700.00 | 22% | $20,000.00 | $4,400.00 |
Form 8606 And NIIT Readout
Employer-plan and all-pre-tax conversions are estimated outside the IRA pro-rata worksheet. Verify the taxable and after-tax basis amounts from plan records and Form 1099-R.
NIIT modeling is turned off. Turn it on when net investment income and MAGI thresholds may matter.
Review Notes
- Estimated conversion tax is higher than the withholding and payments entered; consider withholding or estimated tax payment timing.
Action Checklist
- Confirm whether the conversion source is a traditional IRA, SEP IRA, SIMPLE IRA, employer plan, or all-pre-tax estimate.
- Collect Form 1099-R, Form 5498, prior-year Form 8606, and year-end IRA balance support before filing.
- Model credits, Social Security taxation, premium tax credit, Medicare IRMAA, state tax, and AMT separately if they may apply.
- Confirm no RMD ordering rule applies before executing the conversion.
- Set aside outside cash or estimated tax payments for the projected conversion tax.
Records To Keep
- Form 1099-R showing the distribution or Roth conversion.
- Form 5498 or custodian confirmation showing the Roth IRA conversion contribution.
- Prior and current Form 8606 basis records for nondeductible traditional IRA amounts.
- December 31 traditional, SEP, and SIMPLE IRA balances for the conversion year.
- Estimated tax payment and withholding confirmations.
Important Disclaimer
This calculator provides an educational estimate for planning and comparison only. It is not tax, legal, financial, medical, lending, insurance, payroll, compliance, or institutional advice and it is not an official determination. Rules, rates, eligibility, formulas, and source data can change or depend on facts not captured here. Verify the result against official sources and qualified professional guidance before filing, paying, diagnosing, borrowing, investing, hiring, or making a compliance-sensitive decision.
Professional Review Status
This YMYL page has internal methodology review, but no external credentialed professional review is recorded yet.
- Reliance status
- Credentialed tax review required before professional reliance
- Required credentials
- CPA, Enrolled Agent, licensed tax professional
- Review scope
- tax formulas, jurisdiction assumptions, withholding language, filing-sensitive examples, and compliance caveats
Current reviewer: Iliyas Khan, Internal tax and sales-tax methodology reviewer.
This page is educational planning support. A named CPA, EA, or licensed tax professional should review the page before it is positioned as tax advice or used for filing decisions.
Tax credentialed review: professional reliance limit
This page is educational planning support. A named CPA, EA, or licensed tax professional should review the page before it is positioned as tax advice or used for filing decisions. Results should be treated as a preliminary estimate, not a filing instruction, diagnosis, product recommendation, eligibility decision, or compliance sign-off. Required professional review: CPA, Enrolled Agent, licensed tax professional. Source expectation: Review should cite current IRS, state revenue department, payroll-tax, or official tax authority sources where applicable.
Checked by Iliyas Khan
Roth Conversion Tax Calculator is checked for formula labels, source links, and result limits.
Iliyas Khan, Chief Operating Officer. Updated May 31, 2026. Scope: tax calculators.
Tax credentialed review: Named internal reviewer: Iliyas Khan, Chief Operating Officer. External credentialed professional review is still required before this page is treated as professional advice.
Internal tax and sales-tax methodology reviewer. Review scope: calculator assumptions, labels, source context, workflow clarity, and compliance-sensitive disclaimers.
Relevant review context: CalculatorWallah tax and sales-tax calculator workflow owner; Source-first review of IRS, state revenue, rate, and filing-sensitive references; Compliance-sensitive labels, assumptions, and user-facing disclaimer review.
Required professional credentials: CPA, Enrolled Agent, licensed tax professional. Scope: tax formulas, jurisdiction assumptions, withholding language, filing-sensitive examples, and compliance caveats.
This page is educational planning support. A named CPA, EA, or licensed tax professional should review the page before it is positioned as tax advice or used for filing decisions.
How To Use The Roth Conversion Tax Calculator
Step 1: Enter income before conversion
Start with 2026 AGI before the Roth conversion, choose filing status, and select standard or itemized deduction treatment.
Step 2: Add the conversion source and amount
Choose all-pre-tax, traditional/SEP/SIMPLE IRA with basis, or employer-plan conversion treatment, then enter the planned gross conversion amount.
Step 3: Model Form 8606 basis when needed
For IRA conversions with basis, enter prior nondeductible basis, other IRA distributions, and year-end traditional/SEP/SIMPLE IRA balances.
Step 4: Add NIIT, state tax, and withholding assumptions
Turn on NIIT when net investment income may be exposed by higher MAGI, add an optional state tax rate, and include withholding or estimated payments.
Step 5: Review bracket, cash, and filing flags
Use the bracket impact, tax estimate, outside cash needed, RMD warning, Medicare flag, and record checklist before executing the conversion.
How This Calculator Works
The calculator starts with AGI before the conversion and subtracts either the 2026 standard deduction or the itemized deduction amount entered. The 2026 standard deductions used are $16,100 for single filers, $32,200 for married filing jointly, $16,100 for married filing separately, and $24,150 for head of household.
Then it estimates the taxable part of the conversion. An all-pre-tax conversion is fully taxable. An employer-plan conversion can subtract documented after-tax basis. A traditional, SEP, or SIMPLE IRA conversion with nondeductible basis uses a Form 8606 style pro-rata estimate based on basis, conversion amount, other IRA distributions, and December 31 IRA balances.
Finally, the taxable conversion is stacked on top of pre-conversion taxable income. The calculator compares regular federal tax before and after the conversion, estimates optional NIIT and state tax, subtracts withholding or estimated payments entered, and shows bracket-by-bracket conversion tax.
Roth Conversion Tax Guide: Federal Brackets, Form 8606 Pro-Rata Rules, NIIT, RMD Ordering, Medicare IRMAA, And Cash Planning
Roth conversion tax is a bracket-stacking problem
A Roth conversion generally adds taxable ordinary income on top of the income already on the return. That means the same conversion can be inexpensive in a low-income year and expensive in a year with wages, business profit, capital gains, or large retirement distributions. The most useful planning question is often how much conversion fits inside a target bracket.
| 2026 standard deduction | Amount |
|---|---|
| Single | $16,100 |
| Married filing jointly | $32,200 |
| Married filing separately | $16,100 |
| Head of household | $24,150 |
Roth conversion tax treatment depends on the source account
The calculator separates three common workflows because the taxable amount can be very different. A simple pre-tax conversion is straightforward. An IRA conversion with basis requires Form 8606 discipline. An employer-plan conversion may have separate after-tax basis records. RMD-age taxpayers also need ordering review because an RMD itself is not eligible for conversion.
| Conversion case | Calculator treatment | Record to verify |
|---|---|---|
| All-pre-tax conversion | Entire converted amount is modeled as ordinary income | Useful for simple traditional IRA or 401(k) conversions with no after-tax basis. |
| Traditional, SEP, or SIMPLE IRA with basis | Form 8606 pro-rata estimate | Uses prior basis, other IRA distributions, conversion amount, and December 31 IRA balances. |
| Employer plan with after-tax basis | After-tax basis entered directly reduces taxable conversion | Verify plan records and Form 1099-R before filing. |
| Required minimum distribution | Not eligible for Roth conversion | Take the RMD first, then convert eligible remaining amounts. |
2026 federal bracket stacking example
The single-filer bracket table below shows why conversion sizing matters. If taxable income before conversion is already near the top of a bracket, a large conversion can spill into the next rate. The widget shows the same bracket-by-bracket impact for the selected filing status.
| Single taxable income range | 2026 rate |
|---|---|
| $0 to $12,400 | 10% |
| $12,400 to $50,400 | 12% |
| $50,400 to $105,700 | 22% |
| $105,700 to $201,775 | 24% |
| $201,775 to $256,225 | 32% |
| $256,225 to $640,600 | 35% |
| $640,600 to and above | 37% |
NIIT can rise even though conversion income is not net investment income
Roth conversion income is not itself net investment income, but it increases MAGI. If the taxpayer has dividends, interest, capital gains, rental income, or other net investment income, the higher MAGI can expose more of that investment income to the 3.8% NIIT.
| Filing status | NIIT MAGI threshold |
|---|---|
| Single | $200,000 |
| Head of household | $200,000 |
| Married filing jointly | $250,000 |
| Married filing separately | $125,000 |
Watch for effects outside the conversion line
A good Roth conversion estimate should not stop at regular federal tax. Higher AGI can affect Medicare IRMAA, Social Security benefit taxation, premium tax credit repayment, education credits, student loan interest deduction, charitable deduction floors, state tax, and estimated tax safe harbors. This page flags major review points, but final filing still needs the full return.
Coordinate with the rest of the IRA decision
If the question starts with whether a traditional IRA contribution is deductible, use the Traditional IRA Deduction Calculator. If the taxpayer may still qualify for direct Roth contributions, use the Roth IRA Eligibility Calculator. For whole-return tax modeling after conversion planning, run the Taxable Income Calculator.
Keep the research moving with Traditional IRA Deduction Calculator, Roth IRA Eligibility Calculator, Federal Income Tax Calculator, and RMD Calculator.
Frequently Asked Questions
Related Calculators
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Read guideSources & References
- 1.IRS Publication 590-A - Contributions to Individual Retirement Arrangements(Accessed May 2026)
- 2.IRS Publication 590-B - Distributions from Individual Retirement Arrangements(Accessed May 2026)
- 3.IRS - About Form 8606, Nondeductible IRAs(Accessed May 2026)
- 4.IRS Topic No. 309 - Roth IRA Contributions(Accessed May 2026)
- 5.IRS - Net Investment Income Tax(Accessed May 2026)
- 6.IRS - 2026 tax inflation adjustments(Accessed May 2026)