How much to convert, and in which years

A Roth conversion has a price, and the price is knowable. Every dollar converted is taxed as ordinary income in the year you convert it, federal and state, at the bracket it lands in. The question is never whether to pay tax. It is whether the rate you pay now is lower than the rate you or your heirs would pay later, and whether the years of tax-free growth in between are long enough to make up the difference.

The deadline is December 31. A conversion counts in the calendar year it happens, which means the decision cannot be revisited in the spring the way a contribution can. Most of the work happens between September and November, when the year's income is mostly known and the bracket room left is a real number rather than a guess.

Why the largest conversion is rarely the best one

Converting a large balance in a single year feels decisive and often costs more than it needs to. The conversion itself stacks on top of your other income, so the last dollars converted are taxed at the highest rate you touch. A conversion that fills one bracket this year and repeats for several years often moves the same total at a meaningfully lower average rate.

When a partial conversion answers the question

Full conversion is rarely the goal. The goal is to even out your taxable income across the years between retirement and required minimum distributions, so that no year is wasted in a low bracket and no future year is forced into a high one. For most households that means a sequence of partial conversions, sized each autumn to the room that year actually has.

Before deciding, gather three things: this year's expected income, the balance across your traditional accounts, and the years until required distributions begin. With those, the conversion question stops being abstract and becomes a specific number of dollars, in specific years, at a specific rate.

The last check is the thresholds that are not brackets. A conversion raises the income Medicare uses to set your premiums two years later, it can change how much of your Social Security is taxable, and for anyone under 65 buying health coverage through the marketplace, it can reduce that year's premium subsidy. That is why the right size is often a little below the top of a bracket rather than at it.