Roth Conversion Calculator

Enter the amount you'd convert, your current and expected retirement tax rates, and how you'd pay the conversion tax. You'll see the after-tax value of converting vs not converting, side by side, at your withdrawal horizon.

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How the conversion comparison works

Two futures, after tax. Convert: you pay ordinary income tax on the converted amount now, and what lands in the Roth grows and comes out tax-free. Don't convert: the money stays traditional, grows untouched, and gets taxed at your retirement rate on the way out. The calculator grows both paths to your horizon and compares the only number that matters — what you can actually spend.

The tax-payment toggle changes the math more than people expect. Pay the tax from the conversion and only the after-tax remainder gets Roth shelter. Pay it from separate savings and the full amount is sheltered — but to keep the comparison honest, the don't-convert path then gets to keep that outside cash invested too. We model it in a taxable account where each year's growth is taxed at your current marginal rate, a deliberate simplification: real taxable investing often does a bit better than that (deferred gains, lower capital-gains rates), which would shave some of the convert path's edge. The model is transparent so you can judge it.

The formula

Convert: A × (1 − tnow) × (1 + g)N    Don't convert: A × (1 + g)N × (1 − tret)

A is the amount converted, tnow and tret your marginal tax rates now and in retirement, g the annual growth rate, and N the years until withdrawal (formulas shown for tax paid from the converted funds). Notice something: if tnow = tret, the two expressions are identical — multiplication doesn't care whether you apply the tax haircut before the growth or after. It's the commutative property wearing a tax hat. Every dollar of Roth-conversion advantage comes from the two rates being different, or from sheltering extra money by paying the tax from outside.

Worked example

Convert $50,000 at a 22% current rate, expecting 24% in retirement, 7% growth for 20 years, tax paid from the converted funds.

Convert: $50,000 − $11,000 tax = $39,000 into the Roth, growing to $39,000 × 1.0720 = $150,917.69, all spendable. Don't convert: $50,000 grows to $193,484.22, taxed at 24% on withdrawal = $147,048.01.

Converting comes out $3,869.68 ahead — driven entirely by the two-point rate gap. Flip the rates (24% now, 22% later) and converting loses by a similar margin. Set them equal and the difference is exactly $0.00. The rates are the whole game.

Why the rates end up different — and what to watch

If equal rates make it a tie, the real question is why your retirement rate would differ from today's. The usual suspects: required minimum distributions from large traditional balances can force taxable income whether you need it or not, pushing your later brackets up (see the RMD calculator for how big those get); the widow's penalty — a surviving spouse files single, where the same income hits higher brackets; and plain tax-law uncertainty — current rates are historically low and scheduled brackets have changed many times. All three push toward converting. Pointing the other way: many people simply have less income in retirement and land in lower brackets than their working years.

Two warnings this calculator flags but doesn't compute. First, the bracket bump: the conversion itself is income, so a big one can climb into higher brackets as it goes — your "current marginal rate" may not hold for the whole amount — and can trigger Medicare IRMAA surcharges two years later. That's the argument for converting in slices over several years. Second, conversions are irreversible: since the 2017 Tax Cuts and Jobs Act took effect, a conversion cannot be recharacterized (undone), even if the market drops the week after you convert. Measure twice.

Frequently asked questions

When does a Roth conversion make sense?

When your marginal tax rate today is lower than the rate you expect on withdrawals later — that's the whole engine. Common setups: low-income years (early retirement before Social Security and RMDs start, a sabbatical, a business loss year), or when large traditional balances mean RMDs will force high taxable income later. Paying the conversion tax from separate savings tilts the math further toward converting, because the full amount gets sheltered.

Do I pay taxes on a Roth conversion?

Yes — the converted amount is added to your ordinary income for the year of the conversion, and you pay tax on it at your marginal rate, now. There's no penalty for the conversion itself at any age, but the tax bill is real and immediate. That's the price of never paying tax on that money (or its growth) again.

Can I undo a Roth conversion?

No. The Tax Cuts and Jobs Act eliminated recharacterization of conversions for tax years after 2017, so a Roth conversion is irrevocable — even if the market drops right after you convert and you owe tax on value that no longer exists. Regular annual IRA contributions can still be recharacterized; conversions cannot. Convert with numbers you're sure about.

What is the 5-year rule for Roth conversions?

Each conversion starts its own 5-year clock (beginning January 1 of the conversion year). Withdraw converted principal before that clock runs out and before age 59½, and you owe a 10% penalty on it. Once you're 59½ the per-conversion penalty clock stops mattering, though earnings still need your first Roth account to be 5 years old to come out tax-free.

Should I convert everything at once?

Usually not. A conversion is ordinary income, so a big one can push the top slice into higher brackets — you'd pay 32% converting money you meant to convert at 22% — and can trigger Medicare IRMAA surcharges two years later. Most planners spread conversions over several years, filling up a target bracket each year and stopping at its ceiling. This calculator assumes one marginal rate for the whole amount, so size your conversions to keep that assumption honest.

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