Backdoor Roth IRA Calculator

Calculate backdoor Roth conversion with pro-rata rule. See tax cost if traditional IRA has balance.

By Konstantin Iakovlev · Updated April 2026 · Source: IRS

$

Tax-Free Conversion

$7,500.00

Taxable Amount

$0.00

Tax Cost

$0.00

Pro-Rata Calculation

Existing Pre-Tax IRA Balance$0.00
New Contribution (after-tax)$7,500.00
Total IRA Balance$7,500.00
Pro-Rata Percentage0.00%
Taxable on Conversion$0.00
Tax-Free on Conversion$7,500.00
Tax Cost (24% bracket)$0.00

Use the Backdoor Roth IRA Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Converting traditional IRA funds into a Roth IRA looks simple on paper, but the tax bill depends heavily on whether you already hold pre-tax money in any traditional IRA. The pro-rata rule treats all of those balances as a single pool, and that pooling is what determines how much of your 2026 conversion the IRS counts as taxable.

To find the taxable portion, the tool applies the pro-rata formula: (Total Pre-Tax IRA Balance / Total Traditional IRA Balance) * Converted Amount. That share of the conversion is then taxed at the marginal income tax rate you enter, giving you an estimate of what the move will cost.

The most frequent error is leaving out traditional IRA balances spread across separate accounts, since the IRS aggregates every one of them when applying the pro-rata rule. Knowing your current marginal tax bracket also matters here, because an off bracket throws off the entire tax-cost estimate.

Example: Backdoor Roth Conversion Scenario

  1. 1 Input the total current balance of all your pre-tax traditional IRAs (including SEP, SIMPLE, and rollover IRAs). Enter the amount you plan to convert to a Roth IRA. Finally, input your estimated marginal income tax rate for the year of conversion (e.g., 24% for a 24% tax bracket).
  2. 2 The calculator will first determine the percentage of your total traditional IRA assets that are pre-tax. It then applies this percentage to your conversion amount to find the taxable portion. This taxable amount is multiplied by your marginal tax rate to estimate the immediate tax cost.
  3. 3 You will see the total estimated tax owed on the conversion, the non-taxable (after-tax) portion of your conversion, and the taxable portion of your conversion. This breaks down exactly how your conversion is treated.
  4. 4 This tax cost represents the immediate tax liability incurred by performing the backdoor Roth conversion under the pro-rata rule. The remaining portion of your converted funds, which was previously after-tax, will grow tax-free and be withdrawn tax-free in retirement, assuming all Roth IRA distribution rules are met.

Source: IRS · Last updated: April 2026

Frequently Asked Questions

How does a backdoor Roth IRA conversion work?
A backdoor Roth is a two-step process for high earners above the Roth IRA income limit: contribute to a non-deductible Traditional IRA ($7,000 in 2026), then convert it to a Roth IRA. The conversion is tax-free if you have no pre-tax IRA balances.
What is the pro-rata rule for backdoor Roth?
If you have any pre-tax money in any Traditional, SEP, or SIMPLE IRA, the IRS treats all your IRAs as one pool. The taxable portion of your conversion is based on the ratio of pre-tax to total IRA balances. To avoid this, roll pre-tax IRA money into a 401(k) before converting.
Is the backdoor Roth still legal in 2026?
Yes. Despite proposals to eliminate it, the backdoor Roth IRA strategy remains legal in 2026. The IRS has acknowledged the strategy and there is no legislation currently banning it. However, future tax law changes could restrict or eliminate it.

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