High-3 Average Pay: 3 Essential Rules That Protect Your FERS Pension
The short answer: Your high-3 average pay is the highest average basic pay you earned during any three consecutive years of service. OPM weights it by how long you held each salary rate across those 36 months, so it is not the simple average of your last three annual salaries.
Key takeaways
- The window is any 3 consecutive years of creditable service — usually your final three, but an earlier stretch if your basic pay was higher then (OPM).
- Only basic pay counts: the salary for your position, plus increases from which retirement deductions are withheld. Overtime and bonuses are excluded (OPM).
- The figure is time-weighted. A raise you held for two months moves it far less than one you held for two years.
- With fewer than 3 years of service, OPM averages your basic pay across all creditable service instead (OPM).
How is the high-3 average pay actually calculated?
OPM does not add your last three annual salaries and divide by three. It rebuilds your pay history rate by rate.
The agency identifies every salary rate you held inside the 36-month window, measures how many days you held each one, multiplies each rate by its days, adds the results, and divides by the total days in the window. The output is a single annual figure: your high-3 average pay.
That mechanic is why a promotion late in a career helps less than people expect. The higher rate only counts for the slice of the window you actually held it.
Which pay counts, and which does not?
OPM defines basic pay as the salary you earn for your position, including increases for which retirement deductions are withheld. In practice that means your scheduled rate plus locality pay — both have retirement deductions taken out of every check.
Left out: overtime, bonuses, awards, cash allowances, and any payment with no retirement deduction. Your lump-sum annual leave payment is not basic pay either, so it never raises the high-3.
The practical check is your SF-50s. Every rate change in the window appears on one, and the window is only as accurate as those records.
What does the weighted math look like with real numbers?
Take an employee separating on December 31, 2026, with three rates inside the window:
- $112,000 for 8 months
- $116,200 for 16 months
- $120,300 for 12 months
Weighted: (112,000 × 8) + (116,200 × 16) + (120,300 × 12) = 4,198,800. Divided by 36 months, the high-3 average pay is $116,633.
A simple average of the three rates gives $116,167 — about $466 lower. With 30 years of service at the 1.1% multiplier, that gap is roughly $154 a year in annuity, every year, adjusted by COLAs after age 62.
The number is small here because the rates are close together. It widens sharply when a grade change, a locality move, or a period of leave without pay lands inside the window.
Frequently asked questions
Does the window have to be my last three years?
No. OPM uses the highest three consecutive years. An earlier period wins if your basic pay was higher then — after a downgrade, for example.
Does part-time service change it?
The high-3 is built from your full-time rate, not your part-time earnings. The part-time proration is applied later, to service credit.
Does unpaid leave inside the window hurt me?
Leave without pay generally does not change the rate used; it affects creditable service. See the full high-3 guide for the mistakes that do move the number.
Where can I see the official rule?
OPM publishes it on its FERS information pages, under Computation.
Want to walk through your own figures?
Fed Pilot runs free federal retirement benefits workshops for employees approaching retirement. We go through the high-3 window, the service computation, and the elections that follow, using your own numbers.
