Medicare Part B Premium Calculator
The Medicare Part B premium is the standard monthly amount plus, for higher earners, an income-related monthly adjustment amount (IRMAA) based on your modified adjusted gross income from two years prior. This calculator combines the standard premium with the IRMAA surcharge tier you look up to show your total monthly premium, your annual cost, and the share that comes from the income surcharge. Both amounts are editable so you can enter the current official figures published by the Centers for Medicare and Medicaid Services.
Part B premium formula
Total monthly premium = standard premium + IRMAA surcharge
Total cost this year = total monthly premium * months enrolled
IRMAA surcharge this year = IRMAA surcharge * months enrolled
Standard portion this year = standard premium * months enrolled
IRMAA is a flat monthly dollar amount tied to your income bracket, added to the standard premium. If your income is below the first threshold, the surcharge is zero.
Medicare Part B context
- The standard premium and IRMAA tiers are set annually by the Centers for Medicare and Medicaid Services.
- IRMAA is based on your modified adjusted gross income from two years prior.
- Each income bracket carries a flat dollar surcharge, not a percentage.
- A life-changing event (such as retirement) can let you request a more recent income year.
- If you collect Social Security, the premium is usually deducted from your benefit.
Medicare Part B: frequently asked questions
How is the Medicare Part B premium determined?
Most people pay the standard Part B premium, but higher earners pay an income-related monthly adjustment amount (IRMAA) on top. The surcharge is based on your modified adjusted gross income (MAGI) from two years prior. The Centers for Medicare and Medicaid Services set the standard premium and the IRMAA brackets each year.
What income year does IRMAA use?
IRMAA uses the MAGI reported on your tax return from two years before the premium year. For 2026 premiums, that is generally your 2024 return. If your income has dropped because of a life-changing event such as retirement, you can ask the Social Security Administration to use a more recent year.
Where do I find the standard premium and surcharge amounts?
The standard premium and the IRMAA surcharge tiers are published each year by the Centers for Medicare and Medicaid Services and the Social Security Administration. This calculator takes both the standard premium and your IRMAA surcharge as editable inputs so you can plug in the current official figures.
Is the IRMAA surcharge a percentage or a flat amount?
IRMAA is a set of flat monthly dollar amounts tied to income brackets, not a percentage. Each MAGI bracket has a specific surcharge that is added to the standard premium. If your income is below the first threshold, your surcharge is zero and you pay only the standard premium.
Can the premium be deducted from Social Security?
Yes. If you receive Social Security benefits, your Part B premium (including any IRMAA) is usually deducted automatically from your monthly benefit payment. If you are not yet collecting Social Security, you receive a quarterly bill from Medicare instead.
Official sources
- Medicare: Medicare costs.
- Centers for Medicare and Medicaid Services: CMS.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.