HenryCalc
Backdoor Roth calculator
See the tax cost of a backdoor Roth under the IRS pro-rata rule, based on your pre-tax IRA balance.
Why high earners use the backdoor
Direct Roth IRA contributions phase out at higher incomes, but there is no income limit on converting a traditional IRA to Roth. So high earners make a non-deductible traditional IRA contribution and immediately convert it - the backdoor Roth. With no other pre-tax IRA money, almost none of the conversion is taxable.
What this calculator estimates
Enter your contribution, any existing pre-tax IRA balance, and your marginal tax rate. The tool applies the IRS pro-rata rule and shows the taxable portion of the conversion and the tax you would owe.
The pro-rata trap
The catch is that the IRS pools all your traditional, SEP and SIMPLE IRA money together. If you hold a large pre-tax balance, most of your conversion becomes taxable even though you contributed after-tax dollars. The standard fix is to roll the pre-tax balance into a 401(k) before year-end, which empties the pool and makes the backdoor conversion clean. Use the pro-rata share this calculator shows to decide whether that roll-in is worth doing first.
Frequently asked questions
- What is a backdoor Roth?
- It is a way for high earners who exceed the Roth IRA income limit to still fund a Roth - you make a non-deductible traditional IRA contribution and then convert it to Roth. With no other pre-tax IRA money, the conversion is essentially tax-free.
- What is the pro-rata rule?
- The IRS treats all of your traditional, SEP and SIMPLE IRA balances as one pool. When you convert, the taxable share equals your pre-tax balance divided by your total IRA balance, so existing pre-tax money makes part of the conversion taxable.
- How do I avoid pro-rata tax?
- A common move is to roll existing pre-tax IRA balances into a 401(k) before December 31, which removes them from the pro-rata calculation and lets the backdoor conversion be clean.
Last reviewed January 2026. This calculator provides general educational estimates based on the inputs you enter and simplified assumptions. It is not financial, tax, legal or investment advice, and figures may differ from your actual liability. Verify with a licensed CPA or financial advisor before acting.