401(k) Rollover & IRA Conversion Calculator
Estimate the tax on a Roth conversion and compare the long-term value of Traditional versus Roth.
Net wealth at retirement after adjusting for taxes and opportunity costs.
Moving money between retirement accounts can be tax-free or a taxable event, depending on where it starts and lands. This calculator sorts that out. Tell it the balance, the source account (Traditional 401(k), Traditional IRA, or Roth 401(k)) and the destination (Traditional or Roth IRA), and it flags whether tax is due, estimates the conversion tax, warns about early-withdrawal penalties, and projects how the money grows on each path to retirement. It runs entirely in your browser, so your account balances and income stay on your device.
When tax is due, and how much
A direct rollover that keeps the same tax treatment — Traditional to Traditional, or Roth to Roth — is tax-free, and the tool shows $0 due today. Moving pre-tax money into a Roth IRA is a conversion: the converted amount is added to your income and taxed at your marginal rates. The tool stacks the conversion on your current income to isolate the extra tax it causes, then adds state tax:
Conversion tax = [tax(income + converted) − tax(income)] + converted × state rate
Converting $50,000 on top of $75,000 of income (single, California) adds about $11,190 in federal tax as the money fills the 22% and 24% brackets, plus $4,000 of state tax — roughly $15,190 due for the year. If you pay that tax out of the account itself and you are under 59½, a 10% early-withdrawal penalty applies to the tax portion, which the tool calls out separately. Paying from outside savings avoids the penalty and keeps the full balance compounding.
The long-term comparison
Below the tax figure, two bars project your net wealth at retirement using your years to retirement and expected return. The Traditional path grows the full balance tax-deferred and then taxes withdrawals at the retirement rate you enter. The Roth path grows tax-free, but when you pay the conversion tax from outside funds the tool subtracts the future value of that cash — treating it as money that could otherwise have grown — so the comparison is fair. In the example above, at 7.5% over 25 years the Traditional route projects around $237,800 net and the Roth around $223,900, so the tool leans Traditional; lower a future tax rate or lengthen the horizon and the Roth often pulls ahead. The recommendation simply points to whichever path projects more.
What the model simplifies
This is an estimate for planning, not tax or financial advice. It uses federal brackets and a standard deduction from recent tax years ($15,000 single, $30,000 married, $22,500 head of household), which the IRS adjusts annually. The growth projection assumes one steady return and a single retirement tax rate; it does not model state tax in retirement, required minimum distributions, the five-year Roth rule, Medicare premium (IRMAA) surcharges, or brackets that shift over time. The outside-funds comparison applies a flat 15% capital-gains drag to the taxes paid. Conversions are rarely reversible, so confirm the numbers with a tax professional or advisor before acting.
Frequently Asked Questions
Does this calculator store my balances or income?
No. Everything is calculated in your browser. Your balances, income and tax settings are never uploaded or saved, and reloading the page clears them.
Why does converting to a Roth trigger a tax bill?
Traditional 401(k) and IRA money was never taxed. Converting it to a Roth moves it into an account where future withdrawals are tax-free, so the IRS taxes the converted amount now as ordinary income in the year of the conversion.
Is it better to pay the conversion tax from the account or from savings?
Paying from outside savings usually preserves more retirement growth and, if you are under 59½, avoids the 10% penalty that applies when tax is withheld from the account. The tool shows the penalty and the growth difference for both choices.
Is this financial or tax advice?
No. It is general information for planning only. The projection is simplified and tax figures change yearly, so your real outcome depends on your full situation. Consult a qualified tax professional or financial advisor before converting.