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Backdoor Roth Conversion Calculator

Calculate the taxable portion of your Roth conversion and estimate the federal tax impact using the pro-rata rule.

Quick answer: Estimate the taxable share of a Roth conversion under a simplified pro-rata scenario using the user-entered pre-tax IRA balance and nondeductible basis. Enter Total Nondeductible IRA Basis, Amount You Plan to Convert, Existing Pre-Tax IRA Balance, and Marginal Tax Rate to personalize the estimate. It returns Taxable Portion of the Conversion, Pro-Rata Taxable Percentage, and Estimated Federal Tax on Taxable Portion so you can compare the impact before choosing a next step. Use it to compare long-term value, tax impact, risk, time horizon, and contribution choices.

SWReviewed by SwitchWize Research Desk · Last reviewed July 20, 2026
Taxable Portion of the Conversion
$6,522
Taxable Portion of the Conversion
$6,522
Pro-Rata Taxable Percentage
86.96%
Estimated Federal Tax on Taxable Portion
$1,565
Diagnostic

Because of the pro-rata rule, about 86.96% of your conversion ($6,522) is taxable.

At the entered marginal rate, the estimated federal tax attributable to that taxable portion is $1,565.

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What to do next

About 87% of this conversion is taxable because of existing pre-tax IRA balances. Consider rolling those into a 401(k) before converting to reduce the pro-rata bite.

Your action plan
  1. 1

    Set the target and timeline for this plan

    Estimate the taxable share of a Roth conversion under a simplified pro-rata scenario using the user-entered pre-tax IRA balance and nondeductible basis.

  2. 2

    Check the assumptions before using the result for a high-stakes decision

    Assumptions change the answer, especially when rates, taxes, or timing matter.

  3. 3

    Save the result to Money Map or use the linked next action

    Turn the result into a prioritized action instead of treating it as a one-off number.

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This is an educational estimate, not tax, legal, investment, or lending advice. Tax rules, rates, and eligibility change and depend on your full situation. Confirm with a qualified professional or the provider before acting.

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Frequently Asked Questions

Everything you need to know.

What does an example Backdoor Roth Calculator calculation look like?
Using this calculator's own default assumptions, a total nondeductible ira basis of $7,500, amount you plan to convert of $7,500 and existing pre-tax ira balance of $50,000 produces an estimated taxable portion of the conversion of $6,522 and pro-rata taxable percentage of 87.0%. Enter your own numbers above to see how it changes for your situation.
Why do I have to pay tax on a backdoor Roth if I'm moving my own money?
The tax is triggered because the pro-rata rule looks at your entire IRA pool, not just the money you're converting. Any pre-tax balance in your IRAs means part of your conversion is treated as coming from pre-tax funds, which become taxable income. This applies even if you contributed after-tax money to the conversion: the rule blends all your IRA money together for tax purposes in the year of conversion.
Can I reduce the taxable amount by converting a larger balance?
Converting more money in a single year doesn't change the pro-rata percentage itself, but it does spread the tax across a larger conversion amount. However, a larger conversion also means more total taxable income that year, which can push you into a higher bracket or trigger other tax consequences. The key lever to lower the pro-rata percentage is to reduce your pre-tax IRA balance, usually by converting or rolling it into a workplace retirement plan if eligible.
Is the Backdoor Roth Conversion Calculator free to use?
Yes. SwitchWize calculators are free, and you do not need an account to run scenarios or view the result.
Does using the Backdoor Roth Conversion Calculator affect my credit score?
No. Using a calculator does not trigger a credit check. A credit impact can occur only if you apply directly with a lender, card issuer, or provider.
Are the results personalized financial advice?
No. Calculator outputs are educational estimates based on the inputs you enter. Review assumptions and confirm terms directly with providers before making a financial decision.
What should I do after seeing the result?
Use the recommendation module on this page to compare ira providers, or run Money Map to compare this investing & retirement decision with your other opportunities.
How does SwitchWize choose related offers?
Related offers are matched by the calculator surface (ira) and ranked using SwitchWize data such as rate, fees, trust signals, product fit, and switching friction. Paid relationships do not change organic ranking order.
How fresh are the rates and offers shown?
Rate and offer data is reviewed on a recurring cadence and every offer module shows review context or links to the methodology and disclosure pages.
Where can I see the ranking methodology?
The SwitchWize methodology page explains how rate freshness, editorial review, affiliate disclosure, and category ranking factors work.
Can Money Map use this result?
Yes. Money Map is the broader diagnostic path: it compares savings, mortgage, cards, and debt so you can see whether this calculator result is your highest-impact next move.

Why This Matters

The IRS pro-rata rule treats all your traditional and SEP IRA balances as one pool when you convert to Roth, meaning a conversion is taxed based on the ratio of pre-tax money to total IRA assets. Understanding this taxable share upfront helps you decide whether to proceed with a conversion and budget for the tax bill, since the tax is due in the year of conversion even though the money goes into a tax-free account.

How to Use It

  1. 1Enter your total nondeductible IRA contributions that you've made over time and haven't yet converted.
  2. 2Enter the amount you plan to convert to Roth in this transaction.
  3. 3Enter the total balance across all your traditional, SEP, and SIMPLE IRAs (pre-tax accounts).
  4. 4Enter your marginal federal tax rate to estimate the tax cost of the taxable portion.
  5. 5Review the pro-rata taxable percentage, the taxable dollar amount from your conversion, and the estimated federal tax you'll owe on that amount.
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