Backdoor Roth calculator

Why high earners use the backdoor

Direct Roth IRA contributions phase out at higher incomes, but there is no income limit on converting a traditional IRA to Roth. So high earners make a non-deductible traditional IRA contribution and immediately convert it to Roth - the backdoor Roth. With no other pre-tax IRA money, almost none of the conversion is taxable, and the full amount lands in a Roth IRA to grow and be withdrawn tax-free. The 2026 IRA limit is $7,500 ($8,600 with the age-50 catch-up).

The two-step

1. Contribute up to the IRA limit to a traditional IRA as a non-deductible contribution (you report basis on Form 8606).
2. Convert that balance to a Roth IRA, usually within days.

If you hold no other pre-tax IRA money, step 2 is essentially tax-free because your basis equals the contribution.

The pro-rata trap

The catch is the IRS pro-rata rule: it pools all your traditional, SEP, and SIMPLE IRA balances together and treats every conversion dollar as a blend of pre-tax and after-tax money. The taxable share of your conversion equals your pre-tax balance divided by your total IRA balance.

Worked example

You contribute $7,000 after-tax, but you also hold a $63,000 pre-tax rollover IRA. Total IRA balance = $70,000.

• Pre-tax share: $63,000 ÷ $70,000 = 90%
• Taxable portion of the conversion: 90% × $7,000 = $6,300
• At a 32% marginal rate, tax owed ≈ $2,016

So instead of a clean tax-free backdoor, 90% of your conversion is taxed - even though the dollars you contributed were after-tax.

The fix: empty the pre-tax pool

The standard solution is to roll your pre-tax IRA balance into your employer 401(k) before December 31. The pro-rata rule only counts IRA balances as of year-end, so moving pre-tax money into a 401(k) removes it from the calculation and makes the backdoor conversion clean. Use the pro-rata share this calculator shows to decide whether that roll-in is worth doing first.

Timing and the step-transaction concern

Some advisors space the contribution and conversion by a short period; in practice the IRS has not challenged same-week backdoor Roths, and there is no required waiting period in the rules. The bigger risk is almost always the pro-rata rule, not timing.

The spousal backdoor Roth

The IRA limit is per person, so a married couple can each run their own backdoor Roth - $7,500 each, or $15,000 combined for 2026. Each spouse handles their own IRAs, and the pro-rata rule is checked separately for each, so one spouse’s pre-tax balance does not taint the other’s clean conversion.

State tax and when to skip it

The taxable portion of a conversion is ordinary income federally, and most states tax it too at your state rate - worth factoring in if you live somewhere like California or New York. The backdoor is rarely worth the hassle if you would trigger large pro-rata tax that you cannot avoid by rolling pre-tax money into a 401(k). In that situation, a plain taxable brokerage account is often the simpler choice until your pre-tax IRA balance is cleared.

Common mistakes

• Doing the backdoor while holding a large pre-tax IRA, triggering pro-rata tax.
• Forgetting to file Form 8606 to record the non-deductible basis.
• Rolling pre-tax money into the IRA after the conversion in the same year, which still counts at year-end.

If you have a 401(k) that allows after-tax contributions, pair this with the much larger mega backdoor Roth calculator; to plan converting existing pre-tax savings in a low-income year, see the Roth conversion calculator.