What this calculator includes
The result uses the 2026 CMS and SSA tables. It includes the standard Part B premium of $202.90 per person per month, the Part B income-related monthly adjustment amount, and the separate Part D income-related adjustment. It does not include a Part D plan premium because that amount varies by plan.
For most 2026 determinations, Social Security uses modified adjusted gross income from the 2024 federal tax return. For this purpose, MAGI is generally adjusted gross income plus tax-exempt interest. The tax return year can differ when a return is unavailable or SSA accepts newer evidence after a qualifying life-changing event.
Married filing separately after living with a spouse uses the separate compressed CMS table. Select that exact filing group in the calculator; do not use the individual tiers for that situation.
Why the threshold edge matters
IRMAA is a tiered monthly charge rather than a gradual percentage. Crossing a published income boundary can move the full premium for each Medicare enrollee in the household. The headroom result therefore stops at the upper edge of the current tier; it is not a recommended conversion or gain amount.
The CMS table treats income at the stated boundary as part of the lower tier. Income above that boundary moves to the next tier. Tax returns use whole-dollar reporting, but planning should leave room for corrections and other income.
What to verify before acting
Check the tax year on the Medicare notice, confirm whether both spouses are enrolled, and reconcile AGI and tax-exempt interest to the filed return. If income fell because of a listed life-changing event, review Form SSA-44 instead of relying only on the historical-return result.
Last reviewed August 16, 2026. Calculations use the CMS source of record.