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Roth Conversion Break-Even Age Calculator

This calculator estimates the age at which a Roth conversion can break even when conversion tax is paid from an outside taxable account that is expected to grow at a different rate from the retirement account. The break-even condition occurs when the future tax avoided on the traditional IRA equals the future value of the tax paid at conversion.

The return-rate difference is important: if both pools grow at exactly the same rate, the comparison is driven mainly by the tax-rate relationship and there may be no unique time-based break-even. The page therefore asks separately for retirement-account growth and the return the outside tax-payment funds could have earned.

Calculator inputs

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Result
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Estimated Roth conversion break-even age
Years to break even—
Current-to-future tax ratio—
Annual growth-rate spread—

1. Enter your current age
The calculator adds the modeled break-even duration to this age.

2. Set the conversion-year tax rate
Use the rate applied to the taxable conversion in your scenario.

3. Estimate the future withdrawal rate
This represents the tax that would otherwise be paid on the future traditional IRA distribution.

4. Enter two return assumptions
Use one rate for the retirement account and another for the outside funds used to pay conversion tax.

5. Review whether a finite break-even exists
If current tax is higher and retirement assets do not outgrow the outside funds, the simplified equation may never cross.

Break-even condition: Future withdrawal tax avoided = Future value of conversion tax paid. Years = ln(Current tax rate ÷ Future tax rate) ÷ ln((1 + IRA return) ÷ (1 + Outside-funds return))

If the current conversion tax rate is no higher than the assumed future withdrawal rate, this model treats break-even as immediate. If the current rate is higher and the retirement account has no growth-rate advantage, a finite time-based break-even does not exist.

What the result means

The result is the age at which the modeled tax avoided on the growing retirement balance catches the opportunity cost of paying conversion tax from outside funds.

This is a simplified marginal-rate comparison and does not model tax brackets, Medicare-related effects, Social Security taxation, RMD interactions, or IRA basis.

Given: age 48, current conversion rate 30%, future withdrawal rate 24%, IRA return 7%, outside-funds return 4%.

Calculation: Tax-rate ratio = 0.30 ÷ 0.24 = 1.25. Relative growth factor = 1.07 ÷ 1.04 ≈ 1.028846. Years = ln(1.25) ÷ ln(1.028846) ≈ 7.85.

Result: Estimated break-even age ≈ 55.9.

Why does the calculator need two return rates?

The conversion keeps retirement assets in a Roth while the tax payment comes from outside money. Different growth rates determine how the tax avoided and the tax-payment opportunity cost evolve relative to each other.

When is break-even shown as immediate?

If the modeled conversion tax rate is at or below the future withdrawal tax rate, the simplified tax-rate comparison starts at break-even or better.

Why can there be no finite break-even age?

When the current tax rate is higher and the retirement account does not grow faster than the outside funds, the relative growth needed to overcome that initial disadvantage never appears in this model.

Does the conversion amount matter to the break-even age?

It cancels out of this proportional equation, so the age depends on tax rates and relative growth rates rather than the dollar amount converted.

What tax issues are outside this estimate?

The model does not calculate taxable IRA basis, bracket stacking, required minimum distributions, benefit taxation, surtaxes, or other income-sensitive consequences of a conversion.