About the Backdoor Roth IRA Calculator
High earners who exceed the Roth IRA income limit can still get money into a Roth account using the backdoor Roth strategy: contribute (nondeductible) to a traditional IRA, then convert it to a Roth IRA. The catch is the IRS pro-rata rule — if you hold any other pre-tax money in traditional, SEP or SIMPLE IRAs, part of your conversion becomes taxable, proportional to how much of your total IRA balance is pre-tax versus your new nondeductible (after-tax) contribution.
How it works
- Your nondeductible contribution (2026 limit: $7,500, or $8,600 if 50+) is treated as after-tax basis.
- Your existing pre-tax IRA balance (traditional/SEP/SIMPLE, across all your IRAs, as of year-end) is added to get your total IRA balance.
- The tax-free fraction of any conversion equals your after-tax basis ÷ total IRA balance.
- The taxable amount of your conversion is (1 − tax-free fraction) × the amount you convert.
Assumptions and behaviour
- Follows the same pro-rata / aggregation rule the IRS applies via Form 8606 — all your traditional, SEP and SIMPLE IRAs are combined for this calculation, not just the account you're converting from.
- Assumes the existing balance you enter is the year-end balance across all applicable IRAs, excluding the new contribution.
- If you have $0 in other pre-tax IRA balances, the entire conversion is tax-free (the ideal backdoor Roth scenario).
Limitations
- Doesn't account for investment growth between contribution and conversion (any gain on the contribution before converting is also taxable).
- Doesn't handle 401(k) rollovers into an IRA timing strategies used to avoid the pro-rata rule.
- Estimates only — not tax advice. Confirm with a tax professional and file Form 8606 correctly.
Privacy
The calculation runs entirely in your browser. Nothing is uploaded or stored.
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