Roth Conversion Estimated Tax Planner

Forecast how much cash a Roth conversion will demand beyond current withholding. Blend your conversion amount with marginal federal and state rates, then size the remaining estimated payments needed to satisfy safe-harbor rules and avoid underpayment penalties.

Total dollars you intend to convert to a Roth IRA this tax year.
Marginal federal ordinary income rate that will apply to the conversion.
Combined state and local income tax rate expected on the conversion. Enter 0 for tax-free states.
Defaults to $0. Include federal and state withholding already remitted for the year.
Defaults to $0. Provide your prior-year total tax to compare against the 110% safe-harbor benchmark.
Defaults to 4. Enter how many estimated payment deadlines remain this year.

Educational illustration only. Review tax moves with a credentialed advisor before submitting estimated payments.

Examples

  • $85,000 conversion, 24% federal, 5% state, $10,000 withholding, $42,000 prior-year tax, 3 payments left ⇒ Total estimated tax $24,650.00 USD • Federal portion $20,400.00 USD • State portion $4,250.00 USD • Withholding applied $10,000.00 USD • Balance still to cover $14,650.00 USD • Suggested payment per period (3 remaining) $4,883.33 USD • 110% safe-harbor target $46,200.00 USD • Safe-harbor gap after withholding $36,200.00 USD • Conversion effective tax rate 29.00% • Current withholding covers 40.57% of conversion taxes.
  • $35,000 conversion, 22% federal, 4% state, no withholding added, prior-year tax left blank ⇒ Total estimated tax $9,100.00 USD • Federal portion $7,700.00 USD • State portion $1,400.00 USD • Withholding applied $0.00 USD • Balance still to cover $9,100.00 USD • Suggested payment per period (4 remaining) $2,275.00 USD • Safe-harbor benchmark: add prior-year tax to compare. • Conversion effective tax rate 26.00%

FAQ

Does this include the 10% early withdrawal penalty?

No. Roth conversions avoid the early withdrawal penalty when funds move directly between custodians. The tool only models income tax due.

What safe-harbor percentage should I use?

The calculator defaults to the 110% prior-year tax safe harbor. If your adjusted gross income was under $150,000, replace the prior-year tax input with the 100% target instead.

How do I account for conversion withholding taken at the source?

Include any taxes withheld during the conversion in the withholding field so the balance due reflects cash still owed beyond amounts already remitted.

Can I change the number of estimated payment windows?

Yes. Enter 1–4 in the payment windows field to align with the deadlines remaining in the current tax year.

Additional Information

  • The calculator multiplies your conversion amount by the marginal tax rates provided and subtracts withholding already on file to surface the remaining liability.
  • Prior-year tax is multiplied by 110% to emulate the common safe-harbor threshold for higher earners; adjust the input if a 100% benchmark applies to you.
  • Suggested payments divide the uncovered balance by the number of quarterly deadlines you indicate, keeping amounts even across remaining periods.
  • State tax fields can include local income taxes for an all-in rate if desired.

Related calculators