The raise, and the deduction that shares the envelope
Every October, Social Security announces the next year's cost-of-living adjustment, and every January, beneficiaries discover their net deposit rose by less than the headline. Both numbers are real: the 2.8% COLA for 2026 (announced October 24, 2025) raises the gross benefit, and the Medicare Part B premium, deducted straight from most checks, rose from $185.00 to $202.90 in the same month. The COLA is a percentage of your whole benefit; the premium increase is a flat $17.90 for everyone on the standard rate, which is why smaller checks feel it hardest.
This calculator does both halves honestly: the gross raise the announcement describes, and the net raise your bank account experiences, with the share of your COLA that Medicare consumed stated as a plain percentage rather than left for you to discover in February.
The formula
Share of raise consumed = Premium increase ÷ COLA dollars
Hold harmless is the safety rail: for most premium-deducted beneficiaries, a Part B increase cannot push the net check below last year's, so in low-COLA years the premium increase is capped at your COLA dollars. IRMAA payers and newly enrolled beneficiaries sit outside that shelter.
Worked example
A $2,000 gross benefit with the 2026 COLA of 2.8%: the gross rises to $2,056.00, a raise of $56.00 a month, $672.00 a year.
Then Medicare takes its share: the Part B premium's $17.90 increase means the net check goes from $1,815.00 to $1,853.10: a real raise of $38.10, or 2.10% instead of the headline 2.8%. Put plainly, 31.96% of the raise went to Medicare before it arrived. At 2026's numbers, only benefits under about $639 a month are fully protected by hold harmless.
What the COLA measures, and what it does not
The adjustment is computed from CPI-W, the price index for urban wage earners and clerical workers, comparing the third quarter of this year to the third quarter of last. That makes it automatic and formula-driven (no annual vote, no discretion), and it also fuels the oldest argument in retirement policy: retirees spend more of their budget on healthcare than the CPI-W basket assumes, so the COLA arguably runs a little cool against seniors' actual costs. History says to plan for variety, not a steady number: 0% in 2016, 8.7% in 2023, 2.8% now. The projection on this page compounds a single assumed rate and says so, because pretending to know future inflation is how retirement plans go quietly wrong.
Two neighboring calculators finish the picture. If your income two years ago crossed an IRMAA threshold, your premium and its increase are larger than the standard figures here, and the Medicare IRMAA calculator prices those cliffs to the dollar. And if you have not claimed yet, the COLA is one more reason the claiming-age decision dwarfs most others: adjustments compound on whatever base you lock in, so a larger starting benefit earns larger dollar COLAs every year for the rest of your life; the Social Security break-even calculator weighs that choice properly.