Roth Conversion Breakeven by Age (2026)

A traditional→Roth conversion trades a known tax bill today for tax-free growth later. Whether — and when — that trade wins depends on two competing clocks: the tax you prepay compounds against you from day one, while the conversion's advantages (tax-free compounding, no required distributions, and a lower final rate on money that never has to come out) accrue slowly and accelerate once RMDs begin. This study runs a predefined grid of 756 deterministic scenarios through QuantCalc's parity-tested 2026 tax engine and reports, for each one, the age at which the convert-now strategy's after-tax wealth first overtakes deferring.

How to read this study

Each scenario compares two strategies for the same single filer — $60,000 of ordinary retirement income, a $1,000,000 traditional IRA, and a $250,000 taxable account that pays the conversion tax:

• Convert now: one conversion in 2026, sized to a bracket target, its exact incremental federal tax paid from the taxable account.
• Defer: no conversion; the traditional balance keeps compounding until RMDs force money out at the filer's SECURE 2.0 start age (73 if born 1951–1959, 75 if born 1960 or later), where it is taxed as ordinary income and reinvested taxably.

After-tax wealth in any year values Roth and taxable dollars at face and the remaining traditional balance at a final marginal rate — the rate at which that money will eventually come out, whether through your own later withdrawals or your heirs' (a sensitivity axis: 12% / 22% / 24% / 32%). The breakeven is the first year the convert-now strategy's after-tax wealth is at least the defer strategy's. RMD income along the way is always taxed at the engine-computed bracket rate, not at the sensitivity rate.

Breakeven by age at conversion

The centerpiece table: a single filer converting to the top of the 22% bracket ($61,800 on $60,000 of income for pre-RMD ages, effective cost 20.9%) at 6% nominal growth. Each final-rate column reads: “if the deferred money's eventual rate were this, the conversion pulls ahead at…”. Ages 55–66 were born 1960+ and face RMDs at 75; ages 67–75 (born 1951–1959) face them at 73 — converters already past their RMD age take the year's RMD first and convert on top of it, which is why the conversion amount shrinks and its effective rate rises from age 73.

The SECURE 2.0 seam: age 66 vs 67 in 2026

SECURE 2.0's start-age bands put a seam right in the middle of this grid: a 66-year-old converting in 2026 was born in 1960 and waits until 75 for RMDs; a 67-year-old was born in 1959 and meets them at 73 — just 6 years away instead of 9. In the 12%-final-rate slice, that cuts the wait from 18 years (converting at 66, ahead by age 84) to 16 years (converting at 67, ahead by age 83): the older converter's breakeven arrives sooner after conversion because the defer strategy starts leaking RMD tax years earlier. The full RMD schedule behind this is on the 2026 RMD table page.

Growth: the quiet accelerator

Every channel the conversion wins through scales with the return: more tax-free compounding, more taxable-account drag avoided, bigger future RMDs forced out of the deferred balance. Same slice as above (22% top, 12% final rate), by nominal growth:

Conversion size: what filling a bigger bracket costs and buys

At age 65 ($60,000 income, no RMD yet), the three targets produce very different bills — and, in the low-final-rate regime, very different crossover ages. A small top-off inside the current bracket is cheap per dollar; pushing to the top of the 24% bracket buys a much larger Roth at a higher effective rate:

Ages 63–75: the surcharge a conversion triggers two years later

For each conversion age whose two-year lookback lands at 65 or later, the one-year IRMAA surcharge increase caused by the conversion (single filer, $60,000 base income plus any RMD):

Heirs and the 10-year rule

The final-rate axis is doing quiet double duty: for many converters the deferred balance's “final rate” is not their own but their heirs'. Since the SECURE Act, most non-spouse beneficiaries must empty an inherited traditional IRA within 10 years — often their own peak earning years — so an inherited pre-tax balance can come out at 24–37% marginal rates even if the original owner never left the 12% bracket. An inherited Roth also follows the 10-year clock, but the distributions are tax-free. Read through that lens, the high-final-rate columns above (24%, 32%) approximate the “converting for the kids” case, and they cross over immediately at every age in this grid. This study models the terminal rate as a single number and does not simulate beneficiary-year bracket paths; the Single Life Expectancy Table dataset and inherited IRA RMD calculator cover the distribution mechanics.

Full grid (756 scenarios)

Every scenario: age at conversion (55–75) × target (current bracket / 22% top / 24% top) × growth (4% / 6% / 8%) × final rate (12% / 22% / 24% / 32%). Filter, then click any column to sort. “Advantage at 100” is the convert-minus-defer after-tax wealth gap at the horizon.