Backdoor Roth IRA Calculator 2026 β Pro-Rata Rule Tax Calculator
Calculate how much tax you'll owe on a backdoor Roth conversion. See how the pro-rata rule affects your conversion and what you can do to avoid it.
Pro-Rata Calculation Breakdown
How the Backdoor Roth IRA Works
The backdoor Roth IRA is a two-step process. First, you make a non-deductible contribution to a traditional IRA (no income limits apply to traditional IRA contributions). Second, you convert that traditional IRA to a Roth IRA. If you have no other pre-tax IRA money, the conversion is tax-free because you already paid tax on the contributed funds.
The strategy breaks down when you have existing pre-tax IRA funds. The IRS applies the pro-rata rule (IRC Section 72(e)) which treats all traditional IRA money as a single pool, preventing you from selectively converting only after-tax amounts.
The Formula
Taxable Fraction = Pre-Tax Balance Γ· Total IRA Balance
Taxable Conversion = Conversion Amount Γ Taxable Fraction
Tax-Free Conversion = Conversion Amount Γ (1 β Taxable Fraction)
Tax Owed = Taxable Conversion Γ Marginal Rate
Example
Total IRA balance: $50,000 + $0 basis + $7,500 new = $57,000
Taxable fraction: $50,000 Γ· $57,000 = 87.7%
Taxable conversion: $7,000 Γ 87.7% = $6,140
Tax-free portion: $7,000 Γ 12.3% = $860
Tax at 24% marginal: $6,140 Γ 24% = $1,474
Solution: Roll the $50K pre-tax into your 401(k) first, then convert tax-free.
2026 Direct Roth IRA Income Limits
You need the backdoor strategy if your MAGI exceeds: $161,000 (single, phase-out begins $146,000) or $240,000 (married filing jointly, phase-out begins $230,000). Above these limits, direct Roth contributions are not permitted.
Pro-Rata Avoidance Strategies Comparison
Compare three strategies side by side to minimize taxes on your backdoor Roth conversion
Compare three approaches to handle your pre-tax IRA balance. All scenarios assume the same $7,500 new contribution.
Strategy Comparison β Three Ways to Handle Your Pre-Tax IRA
| Strategy | Taxable This Year | Tax Cost Now | Future Tax-Free Growth | Best For |
|---|