What is a Roth conversion ladder?

It is converting money from a Traditional account to a Roth over several years, paying income tax on the taxable part each year, often in early retirement. After each conversion's own five-year waiting period, that converted principal can be withdrawn without penalty, creating a ladder of accessible funds before age 59 and a half.

What is the pro-rata rule?

If your Traditional IRAs hold both pre-tax money and after-tax basis (non-deductible contributions), you cannot convert only the basis. Each conversion is treated as proportionally pre-tax and basis, by the ratio across your balance, so part is taxable and part is tax-free. This calculator applies that split using your entered basis.

What does this calculator leave out?

Several real costs: IRMAA Medicare surcharges triggered by higher income, more of your Social Security becoming taxable, state income tax, required minimum distributions, and the five-year-rule penalty timing. It also uses a flat marginal rate rather than bracket math. Treat the result as a baseline and check those factors for your situation.

Should I convert up to the top of a tax bracket?

That is the common strategy: convert just enough each year to fill a low bracket without spilling into the next. This tool uses a flat rate and a fixed conversion amount, so to approximate bracket-fill, set the conversion amount to the room left in your target bracket and use that bracket's rate. A tax professional can size it precisely against your other income.

Roth Conversion Ladder Calculator

Estimate the tax of converting a Traditional balance to Roth over several years, including the pro-rata split when the account holds after-tax basis.

A Roth conversion ladder moves money from a Traditional account to a Roth over several years, paying ordinary income tax on the taxable part of each conversion. When the account holds after-tax basis, the pro-rata rule makes each conversion partly taxable and partly tax-free. This calculator estimates the yearly and total tax at a flat marginal rate, and how the remaining balance shrinks as you convert.

X f in

Total conversion tax

$55,000.00

Tax on the taxable portion of all conversions, at the marginal rate.

Total converted to Roth: $250,000.00
Taxable portion: $250,000.00
Tax-free basis portion: $0.00
Remaining Traditional balance: $370,346.86

Remaining balance and cumulative conversions

Assumptions

Each year a fixed amount is converted from the Traditional account to Roth (capped at the remaining balance). The remaining balance grows at the expected return between conversions, using the shared time-value engine rather than a re-derived formula.
The pro-rata rule is applied: when the account holds after-tax basis (non-deductible contributions), each conversion is split in the ratio of pre-tax to total balance. The pre-tax part is taxable; the basis part is tax-free. Basis is a fixed dollar amount that growth does not increase, so it is consumed only as it is converted out.
Tax is a single flat marginal rate on the taxable portion. This calculator does NOT do bracket-fill (choosing the conversion amount to top up a specific tax bracket), which is how many ladders are actually planned; model that by setting the conversion amount yourself and using your expected marginal rate.
NOT MODELED, and each is a real factor that can change the true cost: IRMAA Medicare premium surcharges (a conversion that raises your modified AGI can lift Part B and D premiums two years later, often at sharp cliffs); the Social Security tax torpedo (extra income can make more of your Social Security benefit taxable); state income tax on the conversion; required minimum distributions (RMDs) from the Traditional account; and the Roth 5-year rule (each conversion has its own 5-year clock, and withdrawing converted amounts before it passes, or before age 59 and a half, can trigger a 10 percent penalty).
Also not modeled: growth of the Roth balance after conversion, conversions pushing you into a higher bracket within a year, and any change in tax law. All figures are nominal dollars.
This is an estimate for educational purposes only, not tax advice. Roth conversions are complex and the omitted factors above can be significant. Consult a qualified tax professional before converting.

How it works

A Roth conversion ladder moves money from a Traditional account to a Roth over several years. Each conversion is ordinary income in the year you do it, so you pay income tax on the taxable part, and the converted money then grows tax-free in the Roth.

Each year the calculator converts a fixed amount (capped at what remains), and the rest of the balance grows at your expected return using the shared time-value engine. The tax is the taxable portion times a flat marginal rate.

The pro-rata rule handles after-tax basis. If your Traditional account holds both pre-tax money and after-tax basis (non-deductible contributions), you cannot convert only the basis. Each conversion is split in the ratio of pre-tax to total balance: the pre-tax part is taxable, the basis part is tax-free. Basis is a fixed dollar amount that growth does not increase, so it is used up only as it is converted out.

This tool uses a single flat marginal rate and a fixed conversion amount. It does not do bracket-fill (sizing the conversion to top up a specific tax bracket), which is how ladders are usually planned in practice. To approximate that, set the conversion to the room left in your target bracket and use that bracket’s rate.

Worked example

Convert $50,000 a year from a $500,000 all-pre-tax Traditional balance for 5 years, at a 6 percent return and a 22 percent marginal rate:

Each year: $50,000 is fully taxable (no basis), so the tax is $50,000 times 22 percent = $11,000.
Over 5 years: $250,000 converted, $55,000 in total tax, and the remaining balance grows between conversions to about $370,346.86.

Now add $20,000 of after-tax basis to a $100,000 balance and convert $20,000 a year. The pro-rata rule makes each conversion 80 percent taxable and 20 percent tax-free, so $48,000 of the $60,000 converted is taxable and $12,000 is basis recovered tax-free.

Scope and limitations

This is the part to read carefully, because each omission is a real cost. NOT modeled: IRMAA Medicare premium surcharges (a conversion that raises your modified AGI can lift your Part B and D premiums two years later, often at sharp cliffs); the Social Security tax torpedo (extra income can make more of your benefit taxable); state income tax on the conversion; required minimum distributions from the Traditional account; and the Roth 5-year rule (each conversion starts its own five-year clock, and withdrawing converted amounts before it passes, or before age 59 and a half, can trigger a 10 percent penalty). The tool also uses a flat rate rather than bracket math, and does not grow the Roth balance after conversion. All figures are nominal dollars. This is an estimate for education, not tax advice; Roth conversions are complex, so consult a qualified tax professional before converting.

Sources

Frequently asked questions

What is a Roth conversion ladder?: It is converting money from a Traditional account to a Roth over several years, paying income tax on the taxable part each year, often in early retirement. After each conversion's own five-year waiting period, that converted principal can be withdrawn without penalty, creating a ladder of accessible funds before age 59 and a half.
What is the pro-rata rule?: If your Traditional IRAs hold both pre-tax money and after-tax basis (non-deductible contributions), you cannot convert only the basis. Each conversion is treated as proportionally pre-tax and basis, by the ratio across your balance, so part is taxable and part is tax-free. This calculator applies that split using your entered basis.
What does this calculator leave out?: Several real costs: IRMAA Medicare surcharges triggered by higher income, more of your Social Security becoming taxable, state income tax, required minimum distributions, and the five-year-rule penalty timing. It also uses a flat marginal rate rather than bracket math. Treat the result as a baseline and check those factors for your situation.
Should I convert up to the top of a tax bracket?: That is the common strategy: convert just enough each year to fill a low bracket without spilling into the next. This tool uses a flat rate and a fixed conversion amount, so to approximate bracket-fill, set the conversion amount to the room left in your target bracket and use that bracket's rate. A tax professional can size it precisely against your other income.

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Last reviewed June 2026.