The 2027 COLA Is Almost Official: Why Your FERS Increase Will Be Smaller Than the Headline Number

Cost-of-living headlines this month are good news for retirees—Social Security's 2027 adjustment is tracking toward the mid-3% range, the highest in three years. If you are a FERS retiree, or planning to become one, the number that lands in your annuity statement will likely be smaller than the number in the headline.

That gap is not a mistake. It is a permanent feature of how FERS calculates its own cost-of-living adjustment, sometimes called the "diet COLA."

Where the estimate stands

The Social Security Administration will announce the official 2027 COLA on October 14, 2026, using the average Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W) for July, August, and September 2026 compared with the same months in 2025. With two of the three months already in, independent trackers put the estimate around 3.5%. The Social Security Administration's COLA page publishes the official figure as soon as it is final, and OPM's retirement center applies the same figure to CSRS annuities.

That 3.5%-ish number is what Social Security beneficiaries and CSRS retirees are on track to receive in full. It is not what most FERS retirees will receive.

Why FERS gets a different number

FERS uses a reduced COLA formula once inflation rises above 2%. In plain English:

• CPI increase of 2% or less: FERS COLA equals the full CPI increase—same as CSRS and Social Security.
• CPI increase between 2% and 3%: FERS COLA is capped at 2%.
• CPI increase above 3%: FERS COLA equals the CPI increase minus 1 percentage point.

At a 3.5% CPI-based figure, that third tier applies: FERS retirees would see roughly a 2.5% increase, while CSRS retirees and Social Security beneficiaries see the full 3.5%. This is not a one-year quirk. It is the standing law governing FERS annuity adjustments, and it shows up every year inflation runs above 2%.

The rule inside the rule: your first COLA depends on when you turned 62

There is a second wrinkle that catches new retirees off guard, and it cuts two different ways depending on your age at retirement. (Disability retirees and some special-category and survivor cases follow different rules—confirm your own case with OPM.)

• You retire at 62 or older: you do not wait a full year. You get a prorated COLA in your first December on the annuity roll—1/12 of the annual percentage for each full month you were retired that year. Retire in June, for example, and your first COLA is roughly half the headline FERS figure.
• You retire before 62 and become COLA-eligible only after you turn 62: the opposite applies. Once you become eligible, your first COLA is the full amount for that year—not prorated—even though you weren't retired for the whole year.

Either way, the number that shows up in your first adjustment is easy to misread if you assume every retiree gets the same fraction. Ask HR or OPM which case applies to you before you build it into your budget.

The part of your income that gets no COLA at all

If you are receiving the FERS Special Retirement Supplement while waiting to reach 62, remember that the supplement does not receive a cost-of-living adjustment in any year, at any inflation rate. It is fixed once it is calculated at retirement and stays flat (subject to the earnings test) until it stops at age 62. Only your FERS pension and Social Security benefit get annual COLAs.

That means a household living partly on the supplement should not assume rising inflation lifts every income source evenly. It lifts the pension (at the reduced FERS rate) and, once claimed, Social Security (at the full rate)—but not the supplement.

Why this matters for retirement timing decisions

The diet COLA formula is one more reason that comparing retirement dates purely on starting pension amount can be misleading. Over a 20- or 30-year retirement, a FERS pension compounds more slowly than an equivalent CSRS pension or Social Security benefit whenever inflation runs hot. A TSP balance managed for growth can outpace that over long horizons too—but unlike the FERS COLA, which never goes negative, it carries market risk and is not a guaranteed comparison.

It also affects the classic "retire on FERS pension vs. rely more on TSP" tradeoff. TSP withdrawals do not carry any built-in COLA—you control the amount—while your FERS pension has a built-in, if muted, inflation adjustment. Neither is automatically better; it depends on how you want to sequence guaranteed income against savings you control.

What to do before October 14

• Do not lock in your household budget around the Social Security/CSRS number. If you are FERS, mentally apply the reduced-tier math above until the official figure is out.
• If you are newly retired or retiring soon, check your first-COLA eligibility date. Ask HR or OPM when your first adjustment applies and whether it will be prorated.
• If you rely on the supplement, plan for it to stay flat. Build any inflation cushion from savings or the pension side of your plan, not the supplement.
• Re-run your long-term plan once the official number is announced. In high-inflation years the gap between your FERS COLA and the full CSRS/Social Security figure can be a full percentage point—and that compounds over a multi-decade retirement.

How to use FERSCalc for this decision

Use Calculator Setup to build your baseline plan, then compare projected household cash flow under different long-run inflation assumptions to see how the FERS pension's reduced COLA and the supplement's flat, non-COLA income interact with taxes and TSP withdrawals over time. For more on what the model does and does not include, see How It Works.

FERSCalc is a planning tool, not an official benefit determination. Confirm your own COLA eligibility date, proration, and final annual adjustment amount with OPM once the 2027 figure is official.