Converting pre-tax 401(k)/IRA dollars to Roth means paying tax on the conversion now, in exchange for tax-free growth and tax-free withdrawals later — with no Required Minimum Distributions ever forcing your hand. The hard part isn't understanding the idea; it's knowing how much to convert and which years, since converting too much in one year just pushes you into a higher bracket than you needed to.
Most people's income actually drops the moment they stop working — no more salary, and Social Security and RMDs haven't started yet. That gap, often five to fifteen years long, is usually the lowest-income stretch of your entire retirement. It's also the best window to convert: you can fill up a modest tax bracket (say, the 22% bracket) with conversions, paying tax at a rate you may never see again once RMDs force large, mandatory pre-tax withdrawals later at whatever bracket you're in by then.
Most Roth conversion calculators answer a narrower question than the one that actually matters: "if I convert $X this year, what's the tax?" That's necessary but not sufficient — the actual decision is a multi-decade sequencing problem. Convert too aggressively early and you overpay into a bracket you didn't need to touch; convert too little and RMDs eventually force larger pre-tax withdrawals at a worse rate. It also interacts with things a single-year tool can't see: Medicare IRMAA surcharges (triggered by a two-years-prior income lookback), ACA subsidy cliffs if you're not yet 65, and your Social Security claiming age.
Plan My Retirement models your entire retirement year by year, so a conversion strategy is evaluated the same way you'll actually experience it — against your real income in every future year, not one year in isolation.
Suppose you retire at 62 with $900,000 in a traditional 401(k) and modest other income. Social Security doesn't start until 67, so ages 62–66 are a five-year low-income window.
| Without conversions: RMDs starting at 73 are forced from a larger, fully-grown pre-tax balance | higher future brackets |
| Filling the 22% bracket each year from 62–66 instead | ~$30–40k/yr converted |
| Effect | smaller future RMDs, more of your balance ends up in tax-free Roth |
The right amount depends entirely on your own balances, other income, state taxes, and Social Security timing — which is exactly what the calculator solves for using your actual numbers, not this illustration's.
See it with a 22%-bracket Roth conversion strategy pre-loaded — then adjust every number to match your actual balances and income.
Open the calculator with Roth conversions on →See the FAQ for quick answers on Roth conversions, RMDs, and related topics, or How the Model Works for the full methodology. If you're weighing an early retirement, the Retire at 55 guide covers how Roth conversions fit into bridging the years before Medicare and Social Security. If Social Security timing is the bigger open question, see the Social Security claiming optimizer.