Tax simulator

Backdoor Roth pro-rata calculator

If you have an old pre-tax IRA balance sitting around, converting a fresh nondeductible contribution to a Roth can trigger tax on most of that conversion, because the IRS treats all your traditional, SEP, and SIMPLE IRAs as one pot. This shows how much of your planned conversion is taxable now and what changes if the pre-tax balance were out of the picture, so you can see the size of the trap and the size of the fix.

Background reading: Advanced contribution strategies

Combined pre-tax IRA balance

Total pre-tax dollars across all traditional, SEP, and SIMPLE IRAs. Roth excluded.After-tax (nondeductible) basis

Nondeductible basis already in those IRAs, including the fresh contribution.Intended conversion amount

The amount you plan to convert to Roth this year.Other ordinary income

Sets the marginal rate the taxable portion stacks on.Filing statusDeductionsHow taxable income is estimated from your income.State

Taxable portion of this conversion

$7,500

100.0% of the $7,500 conversion is taxable ordinary income

As is: the pro-rata breakdown

Combined IRA balance$200,000

Pre-tax balance$200,000

After-tax basis$0

Taxable proportion100.0%

Taxable portion$7,500

Nontaxable (return of basis)$0

Estimated tax owed (federal + state)$3,398

If the pre-tax balance were cleared

Taxable proportion0.0%

Taxable portion$0

Nontaxable (return of basis)$7,500

Estimated tax owed (federal + state)$0

Direct Roth route

Income vs. Roth phaseoutAbove (direct route closed)

Phaseout band$153,000 – $168,000

Where this goes next

This shows the taxable portion and the effect of clearing the pre-tax balance; it does not tell you to roll over or convert. That decision is a conversation with a CFP.

Assumptions and simplifications

The IRS aggregates all your traditional, SEP, and SIMPLE IRAs when applying the pro-rata rule; the taxable fraction uses pre-tax balance over total IRA balance.
Tax on the taxable portion is estimated at the marginal rates it stacks into, plus an optional state rate; it excludes other deductions and credits.
The "cleared" view assumes the pre-tax balance is removed from IRAs (for example, rolled into an employer plan); whether that is available or advisable is a personal decision.