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Retirement

Backdoor Roth IRA Calculator

See the tax cost of a backdoor Roth conversion and your projected growth.

Updated July 2026 · Figures verified July 2026 (sources) · Editorial standards

Tax owed on this conversion
$2,016
Net amount converted
$4,984
Projected Roth balance
$37,992
Taxable portion$6,300Pro-rata pre-tax share90%Contribution$7,000

Backdoor Roth details

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Key figures

Conversion tax owed
$2,016
Taxable portion
$6,300
Net amount converted
$4,984
Projected Roth balance
$37,992

Because 90% of your IRA is pre-tax, $6,300 of your conversion is taxable — costing $2,016 in tax.The converted $7,000 grows to $37,992 tax-free over 25 years.

Conversion tax owed
$2,016
By KalkWiseVerified against official sources Updated July 2026

What is the backdoor roth ira calculator?

In short

A backdoor Roth IRA lets high earners contribute to a Roth despite income limits by making a non-deductible traditional IRA contribution ($7,500 in 2026) and converting it. If you have no existing pre-tax IRA, the conversion is tax-free; otherwise the pro-rata rule taxes part of it.

Calculates the tax cost of a backdoor Roth conversion using the IRS pro-rata rule, then projects the tax-free growth of the converted amount.

How to use this calculator

  1. 1Enter your non-deductible contribution amount (up to $7,000, or $8,000 if 50+).
  2. 2Enter your total existing pre-tax IRA balance — this triggers the pro-rata rule.
  3. 3Set your marginal tax rate to estimate the conversion tax.
  4. 4Choose years to retirement and expected return to project tax-free growth.

The formula

taxable=contribution×preTaxIRApreTaxIRA+contribution
tax=taxable×rate
taxable = C × P / (P + C); tax = taxable × rate; FV = C × (1+r)^n
C
— Contribution being converted
P
— Existing pre-tax IRA balance
taxable
— Taxable portion = C × P / (P + C)
rate
— Marginal tax rate
tax
— Conversion tax = taxable × rate

Worked example

The scenario

$7,000 contribution while holding $63,000 in a pre-tax traditional IRA, 32% tax rate.

gives

The result

Pre-tax share = 90%, so $6,300 of the $7,000 conversion is taxable → $2,016 conversion tax; only $700 converts tax-free. (With $0 pre-tax IRA, the whole $7,000 converts tax-free — the 'clean' backdoor Roth.)

Common use cases

  • High earners above the Roth IRA income limit ($165,000 single / $246,000 married in 2025).
  • Investors with no pre-tax IRA balance wanting tax-free Roth growth.
  • Anyone evaluating the pro-rata tax cost before doing a Roth conversion.

Limitations & assumptions

  • The pro-rata rule aggregates ALL traditional, SEP, and SIMPLE IRAs — not just the one you convert.
  • Does not model the step transaction doctrine or timing between contribution and conversion.
  • State taxes on the conversion are not included.

Frequently asked questions

It's a legal strategy where high earners contribute to a non-deductible traditional IRA (up to $7,500 for 2026, or $8,600 if 50 or older), then convert it to a Roth IRA — bypassing the Roth income limits.

Disclaimer: KalkWise calculators are provided for general informational and educational purposes only and do not constitute financial, investment, tax, or legal advice. Results are estimates based on the figures you enter and the assumptions described above. Actual outcomes will vary. Consult a qualified professional before making financial decisions.