Backdoor Roth Pro-Rata Calculator: the facts

1. A direct Roth IRA contribution phases out between $153,000 and $168,000 of income single and $242,000 to $252,000 joint for 2026. A conversion has had no income limit since 2010, which is why the backdoor exists: a nondeductible contribution, then a conversion.
2. The 2026 IRA limit is $7,500, plus $1,100 from age 50. A nondeductible contribution creates basis, reported on Form 8606, that comes out tax-free.
3. The pro-rata rule (§ 408(d)(2)) treats every traditional, SEP, and SIMPLE IRA a person owns as one pool. A conversion carries out basis and pre-tax dollars in the pool's proportion, measured at December 31 with the year's conversions added back; the converter cannot choose to move only the basis.
4. Example: a $7,500 nondeductible contribution converted the same year, with $92,500 in other pre-tax IRAs, is 7.5% basis and 92.5% taxable: $6,938 of income on a $7,500 conversion, and $6,938 of basis stranded in the pool.
5. Employer plans are not in the pool. Rolling pre-tax IRA money INTO a 401(k) that accepts it empties the pool and makes the next conversion clean; a spouse's IRAs are a separate pool.
6. Nothing here turns on the calendar month: a contribution for a year can be made until the following April, but the pool is measured at the December 31 of the year of the conversion.

Educational only, not investment, tax, or legal advice. Results are hypothetical estimates that vary with each use and over time and are not guaranteed accurate or complete. Using this tool creates no client relationship with Considerate Capital, and the site that linked here is not affiliated with it. By using it you agree to the tool terms.