Backdoor Roth IRA Tax Calculator

Estimate conversion income taxes, analyze taxable proportions under the IRS Pro-Rata rule, and plan backdoor Roth contributions safely.

After-tax contribution amount

Total existing pre-tax IRA balance

Sum of Traditional, SEP, and SIMPLE IRAs

Your marginal tax rate

Your current age

years old

Pay taxes from converted funds

Net Roth Converted

$7,000.00

Taxable Portion

0.0%

$0.00

Tax-Free Portion

100.0%

$7,000.00

Estimated Taxes Due

$0.00

Converting $7,000.00 of after-tax Traditional IRA funds to a Roth IRA will result in a total IRA pool of $7,000.00. Under the IRS Pro-Rata Rule: 100.0% of your conversion is tax-free ($7,000.00), and 0.0% is taxable ($0.00). You will owe approximately $0.00 in conversion income taxes. By paying taxes out-of-pocket, the full amount of $7,000.00 goes into your Roth account to grow tax-free.

Net Roth Converted$7,000.00

Pro-Rata Conversion Math Breakdown

Step-by-step breakdown of how the IRS aggregates pre-tax and after-tax assets during conversion
Conversion Step	Mathematical Definition	Resulting Amount
1. Non-Deductible Contribution (After-Tax)	Non-deductible basis added this year	$7,000.00
2. Total Existing Pre-Tax Assets	Total traditional, SEP, and SIMPLE IRAs	$0.00
3. Combined IRA Assets Pool	Step 1 + Step 2	$7,000.00
4. Tax-Free Ratio (Basis Ratio)	Step 1 ÷ Step 3	100.00%
5. Taxable Ratio	100% - Step 4	0.00%
6. Taxable Conversion Amount	Conversion Amount × Step 5	$0.00
7. Estimated Taxes Due	Step 6 × Marginal Tax Rate	$0.00
8. Net Converted into Roth IRA	Conversion Amount - Taxes & Penalty (if rolled in)	$7,000.00

The IRS Pro-Rata Rule Equation

If you have existing pre-tax traditional IRA funds, the tax-free portion of your backdoor Roth conversion is determined by the ratio of your after-tax contribution to your total combined IRA assets:

Tax-Free Ratio = After-Tax Contribution ÷ (After-Tax Contribution + Pre-Tax IRA Assets)

For example, if you contribute $7,000 after-tax but have $13,000 in existing pre-tax IRAs: your total IRA pool is $20,000. Only 35% ($2,450) of your conversion is tax-free. The remaining 65% ($4,550) is taxable, resulting in $1,092.00 in taxes owed at a 24% tax rate.

Frequently asked questions

What is a Backdoor Roth IRA?

A Backdoor Roth IRA is a method high-income earners use to contribute to a Roth IRA when their income exceeds IRS limits. You make a non-deductible contribution to a Traditional IRA and then immediately convert that balance into a Roth IRA.

What is the IRS Pro-Rata Rule?

The Pro-Rata Rule states that you cannot convert only tax-free after-tax contributions to a Roth IRA if you hold other pre-tax traditional IRA balances. The IRS treats all your traditional, SEP, and SIMPLE IRAs as a single pool, taxing the conversion proportionally.

Is there a limit on Backdoor Roth IRA conversions?

While there is an annual limit on contributions to a Traditional IRA ($7,000 for 2026, plus $1,000 catch-up if age 50+), there is no limit on the amount you can convert from a Traditional to a Roth IRA in a tax year.