Medicare Part B Premium Calculator

Most people assume their Medicare Part B premium is a single fixed number everyone pays — and for most beneficiaries, it is: $202.90 a month in 2026. But roughly 8% of Medicare enrollees pay more, sometimes dramatically more, because of a provision called IRMAA — the Income-Related Monthly Adjustment Amount.

IRMAA exists because Medicare Part B is only partially funded by premiums; general tax revenue covers the rest. Since the 1990s and 2000s, Congress has progressively required higher earners to cover a larger share of their own Part B costs, on the theory that beneficiaries who can afford to pay more, should. The result is a five-tier surcharge system: cross an income threshold, and a fixed dollar amount gets added to your premium on top of the standard rate.

The mechanic that trips up the most people is the two-year lookback. Your 2026 Part B premium isn't based on your 2026 income — it's based on your Modified Adjusted Gross Income from your 2024 tax return, the most recent complete tax year Social Security has on file when your 2026 premium is set. This means a big one-time income event — selling a business, a large Roth conversion, a lump-sum retirement payout — doesn't affect your premium immediately. It shows up two years later, sometimes catching retirees off guard when a premium jumps well after the income event itself is long past.

The brackets themselves are cliffs, not a smooth phase-in. A single filer with $108,999 of MAGI pays the standard premium. A single filer with $109,001 — two dollars more — pays $284.10 a month, an extra $81.20, for the entire year. There's no partial surcharge for being just over a threshold; the full tier surcharge applies the moment you cross it. This is exactly why year-end tax planning matters so much for near-retirees and Medicare beneficiaries: a decision to realize $2,000 more in capital gains in November can mean paying nearly $1,000 more in Medicare premiums over the following year, once IRMAA catches up two years later.

One relief valve exists: if your income has dropped since the tax year Medicare is using — because of retirement, a spouse's death, divorce, or several other specific life-changing events defined by the Social Security Administration — you can file Form SSA-44 to request that your premium be recalculated using more current income instead of the two-year-old figure. This is specifically for life changes, though; a general market downturn or a decision to simply spend down savings doesn't qualify on its own.

It's also worth understanding that IRMAA isn't permanent. Because it's recalculated every year from your MAGI two years prior, a high-income year that pushes you into a surcharge bracket doesn't lock you into paying that surcharge forever — if your income drops back down, your premium drops back down two years later, automatically, with no need to reapply.