The IRMAA hit is real but usually small next to the growth
A large conversion can bump you into a higher Medicare premium tier for one year — a real cost, but typically a rounding error next to what an extra decade or two of tax-free growth is worth. See the Medicare IRMAA Calculator to check where a specific MAGI lands on its own, or the RMD Calculator to see how converting now shrinks future required distributions.
Frequently asked questions
Why compare against paying the conversion tax from outside funds?
Paying the tax bill from a separate savings or brokerage account lets the full conversion amount grow tax-free in the Roth — using part of the IRA itself to cover the tax (and paying an early-withdrawal penalty if you are under 59.5) shrinks the amount converted and is almost always the worse option.
Why would I convert if my tax rate stays the same?
Even at an identical rate, converting now and paying tax on today's smaller balance beats paying tax later on a larger, grown balance — the mechanics of pre-paying tax on the principal rather than the compounded total genuinely favor the Roth side, all else equal.
Why does this only show one year of IRMAA impact?
IRMAA is reassessed every year from your MAGI two years prior — a one-time conversion only inflates one year's MAGI, so it only affects one year's premium, two years later, not every year going forward.
Last updated: June 2026