Social Security COLA 2027 is 3.6%: how the number was built
The official 2027 Social Security COLA is 3.6%. The CPI-W math behind it, the 328.746 average, and how it beat our 3.2% to 3.5% projection.
The cost-of-living adjustment that applies to Social Security benefits in 2027 is 3.6 percent. The Social Security Administration announced it on October 14, 2026, the morning the Bureau of Labor Statistics published the September CPI-W, and the formal determination, “Cost-of-Living Increase and Other Determinations for 2027,” is Federal Register document 2026-21796, on public inspection since October 23. It was an arithmetic result rather than a decision, and this page shows how it was built, month by month, including the part where our own projection came up short.
The short answer: the official 2027 COLA is 3.6 percent. The third-quarter 2026 CPI-W averaged 328.746, which is 3.62 percent above the 317.265 average of the third quarter of 2025, and the statute rounds that to the nearest tenth. The increase takes effect with the December 2026 benefit, paid in January 2027. The SSA’s press release puts the average retirement increase at $75 a month and says nearly 72 million beneficiaries will see it; about 7.3 million people receiving SSI will see their increase begin on December 31, 2026. For the separate set of numbers the IRS indexes off a different BLS release, our IRS 2027 inflation adjustments tracker is this page’s companion tracker.
The formula, from the statute
The rule lives in 42 U.S.C. § 415(i). Three details in the actual text matter more than anything in the press coverage:
The index is CPI-W, not CPI-U. The Consumer Price Index for Urban Wage Earners and Clerical Workers covers a narrower population than the CPI-U that generates inflation headlines. The two diverge, sometimes meaningfully, because their spending baskets differ — CPI-W weights gasoline and transportation more heavily, which is why energy prices move the COLA more than they move the number you read about.
The measure is a quarterly average, not a single month. The statute specifies “the arithmetical mean of such index for the 3 months in such quarter”, and the relevant quarter is the one ending September 30. July, August and September carry exactly equal weight. A single hot or cold month moves the result by roughly a third of its own size.
The comparison is against the last year that produced a COLA. For 2027, that is the July–September 2025 quarter.
There is a fourth detail almost nobody explains, and it costs money: once the percentage is applied, benefit amounts that are “not a multiple of $0.10 shall be decreased to the next lower multiple of $0.10”. The rounding always goes down, never to the nearest cent.
The two quarters, closed
The 2027 COLA was measured against the CPI-W average for the third quarter of 2025, a number that never changed:
| Month | CPI-W 2025 | CPI-W 2026 |
|---|---|---|
| July | 316.349 | 327.104 |
| August | 317.306 | 328.481 |
| September | 318.139 | 330.654 |
| Q3 average | 317.265 | 328.746 |
The division is 328.746 ÷ 317.265 − 1 = 3.62 percent, which the statute rounds to 3.6 percent. The SSA’s determination also confirms that the Old-Age and Survivors Insurance and Disability Insurance trust fund ratio, 151.3 percent for 2026, is far above the 20 percent level that can restrict a COLA, so the full formula result applies.
How 2026 unfolded, reading by reading
These are the monthly CPI-W readings that led to the quarter, with the running comparison against the 317.265 base:
| Month 2026 | CPI-W | vs Q3 2025 base |
|---|---|---|
| January | 317.942 | +0.21% |
| February | 319.422 | +0.68% |
| March | 323.500 | +1.97% |
| April | 326.541 | +2.92% |
| May | 328.829 | +3.64% |
| June | 327.075 | +3.09% |
| July | 327.104 | +3.10% |
| August | 328.481 | +3.54% |
| September | 330.654 | +4.22% |
Note what happened in June, because it shaped much of the story: the index fell, from 328.829 to 327.075, and July barely recovered it. That is the part of the COLA that almost no coverage connects. A June inflation report received as good news, with headline CPI down on cheaper energy, is mechanically a smaller Social Security raise, because the benefit is indexed to the very index that fell. Cooling inflation and a larger increase are opposites. September then reversed the pattern, with the index rising 0.66 percent from August to 330.654, and that single reading is what pushed the final answer above everything we had published.
What we projected versus what happened
This page was built to be checked. After the August CPI-W, two-thirds of the quarter was fixed: the July–August average was 327.7925, which sat 3.32 percent above the base. We then laid out scenarios for the one reading still to come, and published a band of 3.2 to 3.5 percent with 3.4 percent as the center of gravity:
| If September had been… | Q3 2026 average | Implied COLA |
|---|---|---|
| Back at July’s level (327.104) | 327.563 | 3.2% |
| Down ~0.2% from August (327.824) | 327.803 | 3.3% |
| Flat, repeating August (328.481) | 328.022 | 3.4% |
| Up ~0.2% from August (329.138) | 328.241 | 3.5% |
The method was right and the projection fell short. The formula, September = 951.795 × (1 + COLA) − 655.585, is exactly the one the SSA applied, and we had noted that a September between 329.047 and 329.999 would round to 3.5 percent. The actual September print was 330.654, above the top of every scenario we ran. Our scenarios assumed September would land anywhere from 0.4 percent below August to 0.2 percent above it; it came in 0.66 percent higher. That puts the official 3.6 percent 0.2 points above our 3.4 percent center and 0.1 point above the top of our band. In other words, we called the direction (a COLA well above the 2.8 percent of January 2026) and the mechanics, but we underestimated the size of the September move, and a reader who planned on 3.4 percent had a raise that was slightly smaller than reality.
Checking the method
The same formula reproduces last year’s result: the Q3 2025 average of 317.265 against the Q3 2024 average of 308.729 gives 2.7649 percent, which rounds to 2.8 percent, exactly the COLA that took effect in January 2026. The method reproduces the official result, and this year it reproduced it again once the last reading was in.
What actually reaches your bank account
The announced percentage is not what your deposit rises by, for three reasons worth separating.
The Medicare Part B premium is deducted first. For most beneficiaries the premium comes straight out of the Social Security payment, and it is announced separately by CMS in November — after the COLA. When the premium rises faster than the COLA in percentage terms, it absorbs part of the raise. In recent years it has absorbed a substantial share, and it is the main reason the increase people see is smaller than the one they read about. The SSA says the 2027 premium information will appear in the Message Center of your my Social Security account in late November.
The rounding goes down. As above, to the next lower ten cents, every time.
Taxes and withholding do not adjust automatically. A higher benefit can push more of it into the taxable range, because the thresholds that determine how much of a Social Security benefit is taxable are not indexed to inflation at all — $25,000 and $32,000, fixed in statute since 1984. A COLA can therefore raise your gross benefit and your tax bill at once. Our guide to the frozen Social Security tax thresholds and the tax torpedo runs the two-tier math under 26 U.S.C. §86, and the broader MAGI guide covers why each program measures income its own way. Supplemental Security Income follows the same percentage by statute, which puts the individual federal rate above $1,000 for the first time; the official amounts and the 2027 payment calendar are in SSI payment 2027. VA disability compensation borrows the same percentage too, but only once Congress passes that year’s COLA act; the projected 2027 chart and the bill’s status are in VA disability rates 2027. Federal civilian and military retirees run on their own statutes: FERS takes a point off anything above 3% (FERS and CSRS COLA 2027), and military retired pay follows the COLA automatically, one point less for REDUX (military retired pay COLA 2027).
The calendar from here
| When | What landed or lands | Why it matters |
|---|---|---|
| July CPI-W: 327.104 (BLS, August 12) | One-third of the answer fixed, at +3.10% | |
| August CPI-W: 328.481 (BLS, September 11) | Two-thirds fixed; our band was 3.2–3.5% | |
| September CPI-W: 330.654; SSA announces 3.6% | The COLA is determined and confirmed | |
| Federal Register publication of notice 2026-21796 (on public inspection since October 23) | The formal determination, with the other 2027 figures | |
| Late November 2026 | CMS announces the 2027 Part B premium; the COLA notice appears online in my Social Security | Determines what is left of the raise |
| December 2026 – January 2027 | Paper notice by mail in December; increase appears in payments | Payment date depends on your birth date |
The same October determination carries the other figures for the year, the ones the SSA indexes to wages rather than prices. Among them is the 2027 contribution and benefit base of $192,300, and the amounts you can earn while collecting before full retirement age without benefits being withheld — the mechanics of that test, and the reason the withheld money is not actually lost, are in our guide to the Social Security earnings test. The rest of the set is in our 2027 Social Security figures tracker.
Two companion pieces pick up where the announcement leaves off. The exact date the increase reaches your account — December 31, 2026 for some beneficiaries, a January Wednesday for most — is worked out in when the first 2027 COLA payment arrives. And because the Medicare Part B premium is deducted straight from the check, the raise that reaches your bank is smaller than the headline percentage; the net math after Part B runs those numbers, and the hold-harmless provision explains the statutory floor that keeps a premium jump from turning the raise negative.
The practical advice is short. The percentage is settled, so the open question is the Part B premium that arrives in November. The SSA says that to receive your COLA notice online in my Social Security you need an account and a paperless-notice sign-up by November 18; everyone else gets the paper notice in December.
Sources
- Social Security Administration, “Cost-of-Living Increase and Other Determinations for 2027,” Federal Register document 2026-21796 (PDF).
- Social Security Administration, “Social Security Announces 3.6 Percent Benefit Increase for 2027,” press release, October 14, 2026.
- Bureau of Labor Statistics, CPI-W (series CWUR0000SA0), September 2026 release of October 14, 2026.
- 42 U.S.C. § 415(i), cost-of-living increases.
Quick answers
What is the 2027 Social Security COLA?
The Social Security Administration announced on October 14, 2026 that the 2027 cost-of-living adjustment is 3.6 percent. It applies to the December 2026 benefit, paid in January 2027, and the formal determination appears in Federal Register document 2026-21796. The press release says retirement benefits will rise by $75 a month on average.
How is the Social Security COLA calculated?
Under 42 U.S.C. 415(i), the increase is the percentage change between the average CPI-W for July, August and September of the current year and the same three-month average from the last year in which a COLA took effect, rounded to the nearest one-tenth of one percent. For 2027 that is 328.746 against 317.265, a change of 3.62 percent, which rounds to 3.6 percent. The index is CPI-W, which covers urban wage earners and clerical workers, not the broader CPI-U in the headlines.
What figure was the 2027 COLA measured against?
The July to September 2025 average of the CPI-W, which is 317.265. It was fixed a year ago. The July to September 2026 average turned out to be 328.746, built from 327.104 in July, 328.481 in August and 330.654 in September.
Did this tracker get the 2027 COLA right?
No. After the August CPI-W we projected a band of 3.2 to 3.5 percent with 3.4 percent as the center. The official figure is 3.6 percent, 0.2 points above the center and 0.1 above the top of the band, because the September CPI-W jumped 0.66 percent from August where our scenarios had assumed anything from a 0.4 percent fall to a 0.2 percent rise.
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