Backdoor Roth pro-rata.
How much of your conversion is taxable.
If you have existing pre-tax IRA funds, your backdoor Roth conversion is partially taxable. The IRS aggregates all your non-Roth IRAs and applies the pro-rata rule. This calculator shows exactly how much.
US-only. The pro-rata rule applies under IRS Form 8606 reporting and IRC Section 408(d).
You contribute $7,500 non-deductible to a Traditional IRA. You also have $67,500 in pre-tax IRA funds from prior rollovers. Total IRA balance: $75,000. After-tax portion: 10%. Taxable portion of conversion: 90%. Converting $7,500: $6,750 is taxable. At 22% federal: $1,485 in taxes. You wanted a tax-free conversion. It cost $1,485 instead.
Include ALL Traditional, SEP, and SIMPLE IRA balances. Roth IRA balances are excluded. The IRS aggregates all non-Roth IRAs for this calculation.
This is your basis on Form 8606: money you contributed after-tax but did not deduct.
What this tool assumes
- Total non-Roth IRA balance = pre-tax balance + after-tax basis. December 31 balance is what counts; Roth IRAs are excluded.
- nonDeductibleRatio = afterTaxBasis / totalIRABalance. taxableAmount = conversionAmount × (1 - ratio). taxFreeAmount = conversionAmount × ratio.
- Federal and state taxes apply to the taxable portion only.
- Solution to pro-rata: roll pre-tax IRA balances into a current employer 401(k) (if the plan accepts incoming rollovers). 401(k) balances are excluded from the IRA pro-rata calculation.
- This tool does not model NIIT or interaction with phase-outs. Consult a CPA for complex situations.
HOW THIS IS CALCULATED
This tool runs entirely in your browser — no data is sent to any server. All formulas use standard financial math. Verify the methodology or inspect the source code in your browser's dev tools.