Medicare looks deceptively simple — Part A is free, Part B has a standard premium — until you’re a higher-income household. Then two things change the math. First, the Income-Related Monthly Adjustment Amount (IRMAA) adds a surcharge to Part B and Part D when your income crosses one of five tier lines, and it’s charged per spouse, every month, for life. Second, if you miss your enrollment window, the late-enrollment penalties are permanent — they don’t expire after a year.
The lifetime cost most people never add up
A married couple paying the standard Part B premium plus a Medigap policy and a Part D plan is looking at real five- and six-figure spending across a 25-year retirement. Layer an IRMAA surcharge on top — even one tier — and you add thousands per year, per spouse. This calculator projects that total so you can see it as one number instead of a line item that creeps up every January.
The enrollment traps
Your Initial Enrollment Period runs the three months before, the month of, and the three months after your 65th birthday. Miss it without qualifying coverage and the Part B penalty is 10% for every full 12 months you were eligible but not enrolled — added to your premium permanently. The most common trap: assuming COBRA counts as active employer coverage. It doesn’t. If you’re working past 65, your Special Enrollment Period runs only eight months after your active employment ends — COBRA does not extend it.
There’s also a one-time Medigap window: a six-month Open Enrollment Period beginning when your Part B starts, during which insurers can’t deny you or price you up for health history. Once it closes, that protection is gone in most states.
What this calculator does
Enter your filing status, birth month and year, current income, and a few coverage assumptions. The tool will show you:
- Your IRMAA tier and the monthly Part B + Part D surcharge it carries
- Your estimated monthly and annual household Medicare cost
- A lifetime projection to your chosen longevity age
- Your enrollment windows — IEP, Medigap OEP, and (if you’re working past 65) your Special Enrollment Period — with any penalty exposure flagged
Coordinating Medicare costs with Roth conversion timing, Social Security claiming, and your withdrawal sequence is exactly the kind of financial advice we provide at T&T Capital Management for households with $500K+ in investable assets. This calculator is the clear-eyed starting point.
Run yours.