Part of our guide to How Your Social Security Benefit Is Actually Calculated
Headlines this summer have put the 2027 Social Security increase at 3.6% or 3.8%. Neither is the number. Both are projections made before most of the data existed.
The 2027 adjustment is announced in October 2026, after September inflation data is published. It is calculated from July, August and September CPI-W compared with the same three months a year earlier. Estimates circulating now rest on one month of that data, which is why they keep moving.
How the number is actually produced
There is no committee and no vote. The adjustment is arithmetic, fixed in law.
The Social Security Administration takes the Consumer Price Index for Urban Wage Earners and Clerical Workers — CPI-W, published by the Bureau of Labor Statistics — averages it across July, August and September, and compares that average with the same quarter of the previous year. The percentage increase is the COLA.
That is the entire mechanism. If the average rises 3%, benefits rise 3%. If it does not rise at all, there is no increase — which has happened, most recently in years when inflation was flat.
Why the estimates keep changing
At the time of writing, only part of the measuring period has been published. Every estimate you see is a forecast of the months still missing.
That is why different organisations produce different numbers from the same data — 3.6% from AARP, 3.8% from the Senior Citizens League — and why each revises its figure as new CPI reports land. They are not disagreeing about the formula. They are guessing at two months of inflation.
Because the calculation uses a three-month average, a single hot or cool inflation report moves the final figure by a fraction of what it moves the headline. September's report matters most, because it is the last one in and the only one nobody has modelled yet.
What it means for a payment
The percentage applies to your benefit before deductions. On a benefit of $2,000 a month, a 3.7% adjustment is about $74 — a figure worth working out on your own number rather than a national average, because Social Security benefits vary enormously with earnings history.
Two things routinely make the increase feel smaller than the percentage suggests.
Medicare Part B is usually deducted from the payment. When that premium rises, it takes part of the raise with it before the money arrives. The COLA is applied to the benefit; what lands is what remains.
The index is not built around your spending. CPI-W tracks the buying patterns of urban wage earners, not retirees, who spend a larger share on healthcare and housing. That mismatch is the reason a separate index for the elderly, CPI-E, is periodically proposed — and it is a live policy argument rather than a settled one.
For last year's figure
The 2026 adjustment was 2.8%, announced on 24 October 2025 and payable from January 2026. That is the number currently in your benefit. Comparing this year's estimate with it tells you the direction of travel; it does not tell you the outcome.
The date that matters
Estimates will keep being published, and each one will be reported as news. The number stops being a guess when SSA announces it in October, after the September CPI report.
Until then, treating a projection as a decision input — for claiming, budgeting or anything else — is treating a weather forecast as a rainfall record.
Related reading
- How your Social Security benefit is actually calculated
- When to claim — 62, full retirement age, or 70
- Social Security spousal benefits
- What is inflation, simply
This is general information, not financial advice — see our disclaimer.
Frequently asked questions
When is the 2027 COLA announced?
In October 2026, after the Bureau of Labor Statistics publishes September inflation data. The 2026 adjustment was announced on 24 October 2025 by the same process.
Is 3.8% the 2027 COLA?
No. It is one organisation's projection. Two of the three months the calculation uses had not been published when that figure was produced, so it can still move in either direction.
How is the COLA calculated?
By comparing the average CPI-W for July, August and September against the same three months of the previous year. The percentage increase is the adjustment. There is no discretion and no vote.
When would a 2027 increase reach my payment?
With the payment for January 2027. The adjustment applies to benefits payable from January, not from the announcement date.
Why does my increase feel smaller than the percentage?
Because Medicare Part B premiums are usually deducted from the payment, and when the premium rises it absorbs part of the raise. The COLA is applied to the benefit; what lands in your account is what remains after that deduction.
Sources
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