Quiet Zeros

Calculators / Saving & investing

Backdoor Roth & the pro-rata rule

The backdoor Roth is simple - unless you already hold pre-tax IRA money, in which case the IRS taxes every conversion proportionally. Here is exactly what your conversion costs, and the escape hatch. Nothing you type leaves this page.

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Every IRA in your name counts, across all custodians, as of Dec 31 of the conversion year. Workplace 401(k)s do NOT count.

Enter $0 to $100,000,000.

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The 2026 IRA limit is $7,500 ($8,600 at 50+).

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Federal + state, on your next dollar - the tax tool shows it.

Taxable share of your conversion

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Tax owed on conversion

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Tax-free share

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Basis left in the IRA

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How the IRS sees every dollar you convert

The arithmetic, step by step

How the pro-rata rule works

The IRS treats all your IRAs as one pot. When you convert, you cannot choose to convert "just the after-tax part" - every converted dollar carries the pot's overall pre-tax percentage:

taxable % = pre-tax money / (pre-tax money + after-tax basis)

With $95,000 pre-tax and a $7,500 non-deductible contribution, the pot is 92.7% pre-tax - so 92.7% of ANY conversion is taxed as income, exactly as if the backdoor did not exist. Form 8606 does this math at filing time; better to see it now.

The escape hatch: the reverse rollover

Pre-tax money sitting in a workplace plan does not count in the formula. If your 401(k) accepts roll-ins (most do), move the pre-tax IRA money into it before December 31 - the pot becomes almost pure basis and the conversion becomes almost tax-free. That single move is usually worth thousands.

Notes

The December 31 balance is what counts - converting in January does not dodge a balance that exists in December. Earnings between contribution and conversion are taxable (convert promptly). Federal treatment; a few states differ slightly.

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