How much should I convert to Roth each year?

Federal income tax brackets are marginal: reaching a higher bracket does not cause every earlier dollar to be taxed at the higher rate. For a bracket-fill comparison, start with projected taxable income before the conversion and subtract it from the top of the bracket you want to examine. The remaining space is one candidate conversion amount; zero and a smaller partial fill are useful comparison cases alongside it.

Taxable income is not the same as gross income or modified adjusted gross income (MAGI). The estimate needs to account for deductions and taxable sources such as wages, pensions, interest, tax-deferred withdrawals, and the taxable part of Social Security. The IRS adjusts bracket and deduction figures over time, so the current official schedule belongs in every annual calculation.

Consider Casey and Morgan, a recently retired couple with taxable savings, traditional retirement accounts, and future Social Security benefits. Instead of assuming that one bracket is automatically best, they could compare the same household plan with three conversion inputs: no conversion, a partial bracket fill, and a fill to the selected bracket boundary.

Each run would keep retirement ages, spending, portfolio assumptions, and claiming choices unchanged. The comparison would track the conversion-year tax, later required minimum distributions (RMDs), Medicare costs, lifetime tax, and remaining assets. A different result would then come from the conversion input rather than from changing several assumptions at once; this example is qualitative and does not claim a winning amount or an invented forecast result.

• Estimate taxable income before any conversion, including the taxable portion of Social Security when applicable.
• Select a current IRS bracket boundary as a comparison ceiling and calculate the unused taxable-income space.
• Test zero, a partial fill, and the full bracket-fill amount under identical plan assumptions.
• Compare the added tax now with later RMDs, Medicare costs, lifetime tax, and ending assets rather than looking only at this year's marginal rate.

Medicare's income-related monthly adjustment amount (IRMAA) uses MAGI from two years earlier to set higher-income Part B and Part D premiums. A Roth conversion generally adds taxable income and MAGI in the conversion year, so an amount that fits inside a federal tax bracket can still cross an IRMAA tier and affect premiums two years later.

Tax brackets and IRMAA therefore create different ceilings. A comparison for someone near Medicare age can include one candidate at the tax-bracket boundary and another below the next relevant IRMAA tier, using current Medicare and Social Security Administration figures. Crossing a tier is not automatically a mistake: the added premiums may or may not outweigh later tax and RMD differences, which is why the interaction belongs in the full comparison.

A bracket boundary captures only federal marginal income tax. Before Medicare, conversion income can reduce ACA marketplace premium credits. After Social Security starts, it can cause more benefits to become taxable. State income tax, capital gains, the source of cash used to pay the tax, and a future surviving spouse's filing status can also change the result.

RMD timing matters too. The IRS says an RMD due for a year must be distributed and cannot itself be converted, so an RMD is part of the year's income before a separate conversion is evaluated. Smaller conversions across several years and a larger conversion in one year can reach the same Roth balance with different tax and premium paths.

RetireGlide treats the annual conversion amount as a proposed scenario input. A deterministic, versioned planning engine calculates taxes, RMDs, IRMAA, projections, and Monte Carlo results; AI never performs that math. AI can help explain the inputs and the engine's output, and no proposed plan change is saved until the user confirms it.

The result is an educational comparison of hypothetical scenarios, not a conversion directive. Assumptions and annually changing tax parameters remain visible so the household can review the source of any difference and verify current figures against the official links below.