2027 Social Security COLA — Projected

The timeline: when this stops being a guess

• Aug 12, 2026BLS releases the July 2026 CPI at 8:30 a.m. ET. One of the three determining months is now known. The plausible band roughly halves.
• Sep 11, 2026BLS releases the August 2026 CPI. Two of three known. At this point a careful projection is usually within about 0.1–0.2 points of the final figure.
• Oct 14, 2026BLS releases the September 2026 CPI. The formula now has every input it needs. SSA has historically announced the COLA the same morning, alongside the new taxable maximum and earnings test amounts.
• Nov 2026CMS announces the 2027 Medicare Part B premium and IRMAA thresholds. Only now can anyone tell you what your net Social Security deposit will be. See our projected 2027 IRMAA brackets.
• Jan 2027The COLA appears in benefit payments, starting with the December 2026 SSI payment and the January 2027 Social Security payments.

One caution on that October date. The 2026 announcement was scheduled for October 15, 2025 and actually came on October 24, 2025, because the government shutdown delayed the September 2025 CPI release by nine days. The same shutdown cancelled the October 2025 CPI outright — a month that simply does not exist in the published series. A COLA that rests on exactly three monthly prints has no redundancy if one of them is disrupted.

The statutory formula, quoted

The baseline — official, and it is the only half we know

These are published CPI-W readings, not estimates.

A check you can run yourself. Divide the two published columns: 317.2647 ÷ 308.7290 = 1.027648, an increase of 2.7648 percent, which rounds under §415(i)(1)(D) to 2.8 percent — exactly the COLA SSA announced for 2026 on October 24, 2025. The same arithmetic applied to the same series reproduces the official answer to the digit. That is the whole reason to trust the method here and to distrust the 2026 half of the table, where the inputs do not yet exist.

What the trend looks like so far

Year-over-year CPI-W through the last published month. Green is published; amber is a month the formula needs and nobody has.

The shape matters more than any single number. CPI-W ran near 2.2 percent through February, accelerated hard into a 4.44 percent May, then gave a chunk of it back in June at 3.52 percent. A run that volatile is precisely the case where extrapolating three months forward deserves a wide band rather than a confident point estimate. The June 2026 index level was 327.075; the quarterly average the formula wants would have to come in at 328.37 to land exactly on 3.5 percent, and at 326.78 for exactly 3.0 percent.

Central projection and band

We ran six carry-forward rules against the same published data rather than picking one and calling it the answer. Each fills July, August and September 2026, averages them, and divides by 317.265.

The six rules span 3.26 to 3.96 percent. We publish a band of 3.0% to 4.0% — wider than the spread of the rules themselves, on purpose. The rules all share one dataset and one blind spot: none of them knows what actually happens in the third quarter. A half-point cushion on each side is the least we are willing to allow for three unobserved months, and even that is not a guarantee.

Corroboration, treated as a data point rather than a verdict. The Senior Citizens League, which publishes a monthly CPI-W-based estimate, put the 2027 COLA at 3.8 percent in its early-August 2026 update, unchanged from its July figure. That sits inside our band, in the upper half. It is not confirmation of anything — TSCL is applying the same statute to the same three missing months, so agreement mostly demonstrates that the formula is unambiguous, not that either projection is right. We computed our figures independently from the BLS series and did not adjust them toward theirs.

What a 0.1-point miss is worth

The average monthly benefit for retired workers was $2,084.40 in June 2026, per SSA's Monthly Statistical Snapshot. Every figure below applies the COLA to that average; your own number scales with your own benefit.

So 0.1 percentage point is worth $2.08 a month, or $25.01 over a year, on that average benefit. The full width of our band — one percentage point — is $20.84 a month, about $250 a year. Scale it: a $3,500 benefit moves $3.50 a month per 0.1 point, roughly $420 a year across the band.

How little it takes to move that. Because the quarter is an arithmetical mean of three months, a surprise of one index point in a single month shifts the quarterly average by a third of a point — which is 0.105 percentage points of COLA, or about $2.19 a month for life on the average benefit. One month coming in a couple of tenths hot or cold is entirely ordinary. That is the mechanical reason a projection built before any of the three months publish cannot be tight, and why the answer genuinely changes on August 12.

And the COLA is not the whole story of what arrives in January. It is a gross figure. What lands in the account is the COLA less whatever the 2027 Medicare Part B premium turns out to be, which CMS does not announce until November.

How the COLA collides with Medicare: the hold-harmless rule

Most people meet the COLA as a net number — the deposit went up by this much — because the Part B premium is withheld from the benefit. The rule governing that interaction is at 42 U.S.C. §1395r(f), and it works in a way that surprises people.

Who is left outside it. The protection is narrower than its reputation. It reaches only people whose Part B premium is deducted from a Social Security or Railroad Retirement benefit, and §1395r(f) expressly withholds it from several groups: those enrolling for the first time that year, people whose premiums are not withheld from a benefit at all, dual eligibles whose premiums are paid by Medicaid, those enrolled solely for immunosuppressive-drug coverage, and — the one that matters most to the readers of a 2027 planning page — anyone whose premium is adjusted under subsection (i), the IRMAA surcharge. Cross an IRMAA threshold and you lose hold-harmless entirely, in both directions.

Why 2027 probably does not test it. Hold harmless only bites when the COLA is small relative to the Part B increase. At our central 3.5 percent the COLA is roughly $73 a month on the average benefit — several times any plausible year-on-year Part B premium rise. It is the low-COLA years that trigger it, and when it does trigger, the cost does not disappear: Part B is funded to a target, so the increase the protected majority does not pay is loaded onto the minority who are excluded. IRMAA payers are in that minority. That is the asymmetry worth planning around, and it argues for watching the projected 2027 IRMAA thresholds alongside this page rather than instead of it.

The second-order effect nobody budgets for. A larger COLA raises your gross benefit, which raises the taxable portion of Social Security, which raises MAGI — and MAGI is what IRMAA is measured on, two years later. The base amounts that decide how much of your benefit is taxable ($25,000 and $32,000) have never been indexed since 1984, so every COLA pushes a little more of the benefit across them permanently. A 3.5 percent COLA is a raise and a slow tax increase at the same time. See how much you can earn before Social Security is taxed and the tax torpedo for where that lands.

Common questions

When is the 2027 Social Security COLA announced?

The Social Security Administration has historically announced the figure on the morning the September CPI report is released. The September 2026 CPI is scheduled for October 14, 2026, so expect the 2027 COLA that day. Treat that as a strong expectation rather than a booked date: the 2026 announcement was scheduled for October 15, 2025 and landed on October 24, 2025 because the government shutdown pushed the September CPI release back nine days.

What is the 2027 COLA projected to be right now?

Our central projection is 3.5 percent, with a band of 3.0 to 4.0 percent. That band is deliberately wide because none of the three CPI-W months that determine the answer have been published. The Senior Citizens League, which tracks the same series monthly, published 3.8 percent in early August 2026 — inside our band, in its upper half.

How is the Social Security COLA calculated?

Under 42 U.S.C. §415(i), the COLA is the percentage increase in the Consumer Price Index for the calendar quarter ending September 30 over the same quarter of the most recent year that produced an increase, rounded to the nearest one-tenth of one percent. §415(i)(1)(G) defines a quarter's index as the arithmetical mean of the three monthly readings. So the 2027 COLA is the July, August and September 2026 CPI-W average measured against the July, August and September 2025 average of 317.265.

Why is a 2027 COLA projection made in August so weak?

Because zero of the three determining months exist yet. July 2026 CPI publishes August 12, 2026; August 2026 publishes September 11, 2026; September 2026 publishes October 14, 2026. Every projection circulating today, ours included, extrapolates a trend across three months of unknown data. A one-index-point surprise in a single one of those months moves the COLA by about 0.105 percentage points.

Does a larger COLA raise my Medicare Part B premium?

Indirectly, yes. The hold-harmless rule at 42 U.S.C. §1395r(f) caps the dollar increase in your Part B premium at the dollar amount of your COLA, but only if your premium is deducted from your Social Security benefit. It does not apply to new enrollees, to anyone paying an IRMAA surcharge under subsection (i), to dual eligibles, or to people who pay Medicare directly. A COLA near 3.5 percent produces roughly $73 a month on the average retired-worker benefit, far more than any plausible Part B increase, so hold harmless would not bind for most people in 2027.