IRMAA Medicare Surcharge Calculator

Legal basis: 42 U.S.C. §1395r; Social Security Administration IRMAA rules (MAGI tiers, two-year lookback) · checked 2026-10-04 · Rates and limits change — verify the current figures.

IRMAA - the income-related monthly adjustment amount - is the surcharge higher-income Medicare beneficiaries pay on top of the standard Part B and Part D premiums. It was created under the Medicare Modernization Act and operates through Section 1395r of the Social Security Act: once your income crosses a threshold, a sliding-scale surcharge is added to every monthly premium for both physician coverage (Part B) and prescription drug coverage (Part D). Roughly the top seven or eight percent of beneficiaries pay it.

The trigger is modified adjusted gross income, which for this purpose is your adjusted gross income plus tax-exempt interest, and the measurement is famously lagged: the premiums you pay in a given year are set by the MAGI on your tax return from two years earlier. Beneficiaries newly enrolled in 2026 are charged based on their 2024 return. This two-year lookback means a one-time income spike - a large Roth conversion, a business sale, a year of capital gains - keeps raising your premiums for two years after the money arrived, and also that retirement often lowers them two years later.

The tiers are steep rather than gradual. Income up to the first threshold pays nothing extra; cross it by even a dollar and the entire Part B and Part D surcharge for the next tier applies for a full year, then larger amounts at each further threshold up to the top tier. Thresholds are indexed annually and the surcharge dollar amounts are recalculated every year from the standard premium, so both sets of figures change constantly - this calculator makes the thresholds inputs and offers the surcharge schedules as selectable sets to be verified.

Two things are worth knowing if the result surprises you. First, the Social Security Administration will reopen an IRMAA determination for a life-changing event such as retirement, a marriage, divorce, or the death of a spouse - filing Form SSA-44 with documentation can drop you to a lower tier immediately. Second, because the lookback is two years, the income you recognize this year sets the premiums two years out, which is exactly why bracket-managed Roth conversions and capital-gain timing are standard IRMAA planning tools.

This calculator is an educational estimate, not tax, medical, or financial advice. IRMAA thresholds and surcharge amounts change every year, and the schedules included here must be verified against the current-year SSA or CMS notice. Confirm your determination and any appeal with the Social Security Administration or a CPA or fiduciary adviser.