Roth Conversion Calculator
Compare converting a Traditional balance to Roth today against leaving it Traditional.
Estimates only, not financial, tax, or legal advice. See our Terms and Privacy Policy.
Converting a Traditional retirement balance to Roth means paying ordinary income tax on the converted amount today, in exchange for tax-free growth and tax-free withdrawals later. Leaving it Traditional defers that tax until withdrawal, taxed at whatever rate applies then. This calculator compares both paths on an after-tax basis so the trade-off is a concrete dollar figure instead of a guess.
The comparison depends heavily on your Federal Income Tax Bracket today versus your expected bracket in retirement, and the balance itself needs somewhere to grow either way, see this site's Retirement Calculator for the broader savings picture this decision fits into.
How does this calculator work?
Enter the Traditional balance you're considering converting, your current marginal tax rate (what you'd pay on the converted amount as ordinary income this year), and your expected tax rate in retirement (what the Traditional balance would otherwise be taxed at on withdrawal).
Enter how many years the money would grow before you need it, an assumed investment return applied identically to both paths, and whether you'd pay the conversion tax from outside cash or from the balance itself.
The calculator computes the conversion tax cost (balance × current marginal rate), then grows two separate balances at the same assumed return: the Roth path (starting principal reduced only if you chose to pay the tax from the balance itself, then growing tax-free) and the Traditional path (the full original balance growing tax-deferred, then reduced by the retirement tax rate at the end).
Comparing the two final after-tax figures gives the net advantage: positive means converting to Roth came out ahead, negative means staying Traditional did.
Worked example
A $100,000 Traditional balance, converting at a 24% current marginal rate versus an expected 22% retirement rate, growing for 20 years at 7%, paying the conversion tax from outside cash.
- Conversion tax cost today
- $24,000
- Roth balance after 20 years
- $386,968
- Traditional after-tax balance after 20 years
- $301,835
- Net advantage
- $85,133 in favor of Roth
How the numbers work
Paying the $24,000 conversion tax from outside cash means the full $100,000 converts and grows tax-free, reaching $386,968 after 20 years at 7%.
The Traditional path grows the same $100,000 to $386,968 pre-tax (the identical growth rate), but loses 22% to tax on withdrawal, leaving $301,835 after tax, $85,133 less than the Roth path.
Converting tends to win when your current tax rate is lower than (or equal to) your expected future rate, and when you can pay the conversion tax from outside funds rather than shrinking the converted balance itself. When the tax-rate relationship reverses, so does the advantage, run your own numbers rather than assuming either direction.
Roth Conversion Calculator glossary
- Roth Conversion
- Moving funds from a Traditional (pre-tax) retirement account into a Roth account, paying ordinary income tax on the converted amount in the year of conversion.
- Marginal Tax Rate
- The tax rate applied to the next dollar of income, the rate a Roth conversion is taxed at since it's added on top of your existing income for the year.
- Tax-Deferred vs. Tax-Free
- A Traditional account defers tax until withdrawal, taxed as ordinary income then. A Roth account is funded with already-taxed money and grows and withdraws entirely tax-free, assuming the rules for a qualified withdrawal are met.
Roth Conversion Calculator FAQs
Why does paying the conversion tax from the balance itself change the result?+
If tax comes out of the converted balance, less principal actually makes it into the Roth account to grow tax-free, which is a real drag on the outcome compared to paying from outside cash. Choosing "the converted balance itself" in this calculator reduces the starting Roth principal by the tax cost before any growth is applied.
Does this account for the 5-year rule or other conversion-specific rules?+
No, this calculator focuses purely on the tax-rate and growth trade-off. Actual conversions are subject to IRS rules like the 5-year holding period for penalty-free withdrawal of converted funds and the pro-rata rule if you hold both pre-tax and after-tax dollars across your IRAs.
the IRS's Roth IRA conversion FAQCan a Roth conversion affect anything else on my tax return?+
Yes. The converted amount counts as income in that year, which can push you into a higher bracket, increase how much of your Social Security benefit is taxable, or (for Medicare-age filers) raise Medicare Part B and D premiums two years later through IRMAA. None of those secondary effects are modeled here.
Is a Roth conversion reversible if I change my mind?+
No. Conversions made after 2017 can no longer be recharacterized (undone) for tax purposes, so it's worth being confident in the decision, or converting a smaller amount, rather than treating it as a trial run.