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The basics
Part B covers physician and outpatient services; Part D is prescription-drug coverage. Their real premiums are not one universal combined bill: Part B has a standard premium, while actual Part D premiums vary by plan. The forecast combines the 2026 standard Part B premium with the Part D national base beneficiary premium as a transparent planning placeholder.
Illustrative numbers
The 2026 starting placeholder
Part B, monthly$202.90
Part D base, monthly$38.99
One person, annual$2,902.68 before supplement or IRMAA
A two-person household with both people enrolled starts at $5,805.36 a year before any selected Medigap or Advantage premium and before an income-related surcharge.
Calculation transparency
How it works in MoneyWhatIf
- 01
The switch is on by default. Each person is charged from the plan year containing their 65th birthday; the current partial plan year is prorated to the months the projection contains.
- 02
The 2026 starting values are $202.90 a month for standard Part B and $38.99 for the Part D national base beneficiary premium. A user-entered monthly supplemental amount is added per enrolled person.
- 03
The combined premium grows at plan inflation plus two percentage points each year. This is a healthcare-cost assumption, not a forecast of future published premiums.
- 04
IRMAA is calculated separately from household MAGI two years earlier and added for each enrolled person. It is documented in the related IRMAA guide.
- 05
The Medicare schedule also lets a healthcare spending category step down as each person turns 65, avoiding a duplicate private-cover cost when that option is selected.
Keep in mind
Model limits
The Part D national base beneficiary premium is a statutory input to premium calculations, not the premium every drug plan charges. Actual Part D and Medicare Advantage prices vary by plan and location.
The base row does not model Part A premiums, deductibles, coinsurance, copays, uncovered care, Extra Help, employer or retiree coverage, or out-of-pocket limits.
Late-enrollment penalties, exact enrollment months, appeals, and plan changes are not modeled. Turn the setting off only when another spending category already includes these premiums.
This explanation documents the planning model. It is educational, not individualized tax, legal, Medicare, or investment advice.
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The words behind it
Related financial terms
Plain-English definitions, with 2026 figures and worked examples, from the financial terms glossary.