Backdoor Roth IRA pro-rata calculator

How it works

This runs IRS Form 8606, Part I exactly: total basis (this year's nondeductible contribution plus any prior-year basis) divided by the value of all your traditional/SEP/SIMPLE IRAs on Dec 31 plus the year's distributions and conversions, rounded to 5 decimal places and capped at 100%. That fraction is the tax-free share of whatever you convert -- a 401(k) or Roth IRA balance doesn't count toward it. With $0 in other pre-tax IRAs, a same-year conversion is 100% tax-free; with $93,000 sitting in an old rollover IRA, a $7,000 conversion is only 7% tax-free ($6,510 taxable). Full math: the pro-rata rule guide.

Worked examples

• The backdoor Roth IRA pro-rata rule: when it's NOT tax-free (Form 8606, worked)
• Roth or traditional 401(k)? Which leaves more at 65, by tax rate now and in retirement