Backdoor Roth IRA

📌 What Is a Backdoor Roth IRA?

A Backdoor Roth IRA is a perfectly legal tax strategy that allows high-income earners to contribute to a Roth IRA even when their income exceeds the IRS's direct contribution limits. For 2025, single filers earning over $161,000 and married couples earning over $240,000 are phased out of direct Roth contributions — but the backdoor route bypasses those limits entirely.

The process involves two steps: first, you make a non-deductible contribution to a Traditional IRA (which has no income ceiling), and then you immediately convert that balance to a Roth IRA. The converted funds grow tax-free forever, and qualified withdrawals in retirement are completely tax-free — one of the most powerful long-term tax advantages available to high earners.

The complexity — and the main reason you need a calculator — is a rule called the Pro-Rata Rule. If you have any existing pre-tax IRA balances (from a rollover, a SEP IRA, or a deductible Traditional IRA), the IRS requires you to treat all your IRA money as a single pool when calculating how much of the conversion is taxable. Ignoring this rule is the most expensive mistake people make with this strategy.

👤 Who Is This Calculator For?

• High-income professionals (physicians, attorneys, senior tech workers) who are phased out of direct Roth IRA contributions
• Self-employed individuals with SEP IRAs who want to understand their pro-rata tax exposure before converting
• Married couples filing jointly who have recently crossed the Roth income threshold due to a raise or bonus
• Anyone planning a "mega backdoor Roth" through a 401(k) who first wants to model the simpler IRA version

🛠️ How to Use This Calculator

1. Enter your planned contribution: For 2025, the IRA contribution limit is $7,000 ($8,000 if you're 50 or older).
2. Enter your existing pre-tax IRA balance: This is the most critical field. Add together all Traditional IRA, SEP IRA, and SIMPLE IRA balances you hold at any brokerage. If you have zero existing pre-tax IRAs, your conversion is entirely tax-free.
3. Enter your marginal tax rate: This is the tax bracket that applies to your next dollar of income. Use a tax bracket table or check last year's return.
4. Review the results: The calculator shows your Pro-Rata percentage (what portion of the conversion is taxable), the taxable dollar amount, and the estimated tax bill for the conversion.

📐 The Pro-Rata Rule Formula

If your existing pre-tax IRA balance is $0, the taxable percentage is 0% and the conversion is entirely tax-free — the ideal scenario for this strategy.

💡 Real-World Example

Sarah earns $220,000 as a physician and is phased out of direct Roth IRA contributions. She has a $63,000 SEP IRA from her previous practice. She contributes a new $7,000 non-deductible contribution to a Traditional IRA and converts it to a Roth.

Pro-Rata Calculation: Pre-tax balance = $63,000. Total IRA pool = $63,000 + $7,000 = $70,000. Taxable % = 63,000 ÷ 70,000 = 90%. Taxable amount = $7,000 × 90% = $6,300. At a 32% bracket: tax owed = $2,016.

Sarah would owe $2,016 in taxes on her conversion. To avoid this, she should look into rolling her SEP IRA into her current employer's 401(k) — a move called "IRA rollover to eliminate pro-rata" — before doing the conversion.

⚠️ Limitations of This Calculator

• This calculator uses a simplified pro-rata model and assumes the conversion and contribution happen within the same tax year.
• It does not account for state income taxes, which can significantly add to the tax bill in states like California or New York.
• It does not calculate the long-term tax-free growth benefit of the Roth conversion — consult a retirement calculator for that projection.
• Inherited IRAs are subject to entirely different rules and are not factored into this tool.
• Always confirm your exact tax liability with a CPA or enrolled agent before executing a conversion.