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Retirement · Bracket-Fill Planning

Roth Conversion
Window Calculator

Between the year you stop working and the year required distributions begin, there is usually a stretch where your taxable income sits well below the top of a bracket. This calculator measures that window in two directions at once. It finds how much room you have before you spill into the next ordinary bracket, and separately how much room you have before you cross the next IRMAA threshold and raise your Medicare premium two years from now. The smaller of the two is your window. This tool answers how much room you have this year, not whether a Roth or a Traditional account is the better home for the money.

Data: 2026 vintage · Rev. Proc. 2025-32 brackets · 2026 CMS IRMAA thresholds and premiums

Your Situation STEP 1
Used only to flag whether IRMAA is relevant yet
Pension, interest, taxable Social Security, RMDs, wages
Pre-filled from the 2026 standard deduction
Added back for IRMAA MAGI, not for taxable income
Counted in IRMAA MAGI, taxed separately from this conversion
The bracket you are willing to fill to the top of
Hard cap on the conversion
IRMAA is charged per enrollee
Uncheck to see bracket room only
If unchecked, the tax is withheld from the conversion itself
Constants Panel EDITABLE
Also used for HoH, see FLAGS
SECURE 2.0 sec. 107
Recommended Conversion
--
Binding cap: --
Federal Tax On Conversion
--
Blended rate on the amount converted
IRMAA Cliff Cost If Crossed
--
Annual, two years from now, per household
Current Position
Current taxable income--
Current IRMAA MAGI--
Current IRMAA tier--
The Three Caps
Cap A, room to top of target bracket--
Cap B, room to next IRMAA threshold--
Cap C, convertible balance--
Recommended conversion--
Tax & Cliff Impact
Federal tax on the conversion--
Blended rate on the conversion--
Net amount landing in the Roth--
Annual IRMAA cost of crossing the next threshold--
Unused bracket room left on the table--
Years until required distributions--
Cumulative room if repeated each year--
This is an illustrative estimate, not tax or Medicare advice. Treatment depends on your full facts and on current IRS and CMS guidance, which can change. Consult a CPA, financial planner, or tax attorney.
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