What is the pro-rata rule?

The IRS treats all your traditional IRA money as one pool. If you have pre-tax IRA balances, a proportional share of any conversion is taxable — you can't just convert the after-tax portion.

How do I avoid the pro-rata rule?

Roll existing pre-tax IRA balances into a 401(k) (if your plan allows) before doing the conversion, leaving only the non-deductible contribution to convert tax-free.

How much can I contribute to a backdoor Roth in 2024?

The traditional IRA contribution limit is $7,000 in 2024, or $8,000 if you're 50 or older — that's the amount you can convert each year.

Is the backdoor Roth legal?

Yes. The IRS has acknowledged the strategy, and it remains legal as of 2024. However, always follow the pro-rata rule and report the conversion correctly on Form 8606.

Backdoor Roth IRA Calculator

By the KalkWise Editorial Team Reviewed for accuracy Updated June 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 ($7,000 in 2024) 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

1Enter your non-deductible contribution amount (up to $7,000, or $8,000 if 50+).
2Enter your total existing pre-tax IRA balance — this triggers the pro-rata rule.
3Set your marginal tax rate to estimate the conversion tax.
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, $0 existing pre-tax IRA, 32% tax rate, 25 years, 7% return.

gives

The result

Taxable portion: $0. Conversion tax: $0 (clean backdoor Roth). Projected: ~$38,000 tax-free.

Common use cases

High earners above the Roth IRA income limit ($161,000 single / $240,000 married in 2024).
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, 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.

Backdoor Roth details