IRMAA Calculator

IRMAA in plain English

Medicare is not free. Everyone on Part B pays a monthly premium, and everyone on Part D pays a plan premium. If your income is above a set threshold, you pay a surcharge on top called IRMAA, which stands for Income-Related Monthly Adjustment Amount. IRMAA hits Part B and Part D separately, and it can add hundreds of dollars per month to your Medicare bill.

The 2-year lookback

Social Security uses your Modified Adjusted Gross Income from your tax return 2 years ago to set this year's IRMAA. Your 2025 IRMAA is based on your 2023 return. A big income year, from a business sale or a Roth conversion, will follow you into your Medicare premiums for the following two years. Plan accordingly.

The cliff, not a slope

Unlike income tax brackets, IRMAA is a series of cliffs. Cross a threshold by even one dollar and your monthly surcharge jumps to the entire next tier for the whole year. For a couple, the swings between tiers can be a few thousand dollars per year. Being $500 over a threshold is genuinely expensive; being $500 under costs nothing.

What counts as MAGI here

For IRMAA, MAGI is your Adjusted Gross Income plus tax-exempt interest (typically from muni bonds). Roth conversions count. Capital gains count. RMDs count. Tax-free Roth withdrawals do not. Return of principal does not. Municipal bond interest does count, even though it is tax-free for regular tax purposes.

Common IRMAA triggers

Watch out for the year you take Social Security and start RMDs; the year you sell a rental property or business; a bunched charitable year followed by a big Roth conversion; and the year one spouse dies, when the surviving spouse files single and the thresholds effectively cut in half. Every one of these can silently push you into a new IRMAA tier.

Ways to manage IRMAA

The best IRMAA planning happens years in advance. Do Roth conversions before Medicare enrollment, when there is no IRMAA cost. Use Qualified Charitable Distributions once you are 70.5 to reduce RMD income. Spread large realizations across multiple tax years. Harvest losses. If you had a genuine life-changing event, such as retirement or the loss of a spouse or a pension, file Form SSA-44 to appeal.

This calculator uses the 2025 IRMAA brackets. The Social Security Administration updates them each fall for the following year.