High-3 Average Salary Calculator

How this is calculated

Your high-3 — OPM calls it your average salary — is the largest annual rate you get by averaging your basic pay over any 3 consecutive years of creditable service. It is the base of the annuity formula, so a mistake here is multiplied by every year of service you have.

Σ (each rate of basic pay × days held) ÷ 1,080 days

Time-weighted, not year-by-year

The most common way to get this wrong is to take your salary for each of three calendar years and average the three numbers. OPM does not do that. It weights every rate by the number of days you actually held it. A raise that took effect in October counts for roughly a quarter of that year, not all of it — which is why the answer usually lands below the salary you are earning on the day you leave.

The 360-day year

Federal service time is counted on a 360-day year of 30-day months, so 3 years is exactly 1,080 days regardless of which months it spans. The 31st of a month counts as the 30th. This calculator uses the same arithmetic, so its day counts match the ones on a service computation.

Highest, not last

The window is the highest 3 consecutive years, not the final ones. For most careers those are the same period, and the tool says so. They come apart when pay falls: a downgrade, a move from a high-locality area to a lower one, a special salary rate that ends, or a return from a temporary promotion. In those cases an earlier period is the higher one and OPM uses it — this calculator tests every possible 3-year window and reports the best, naming its start and end dates so you can check them.

What counts as basic pay

Basic pay is the rate retirement deductions come out of. It includes locality pay and most special salary rates. It excludes overtime, bonuses, cash awards, allowances, and any pay you received without retirement withholding.

What this does not model

Deliberately out of scope, because each would need a pay history this form does not ask for:

• Breaks in service. The dates you enter are treated as one continuous period of creditable service. If you left and came back, compute the periods separately, or treat the result as approximate.
• Leave without pay and intermittent service, which push the window further back because the 3 years must be 3 years of actual creditable service.
• Part-time proration. Part-time service uses the full-time rate here, which is correct — but the resulting annuity is then prorated, and that step happens outside this tool.
• Deposits and redeposits for service where deductions were never made or were refunded.

Sources

• OPM CSRS/FERS Handbook, Chapter 50 — Computation of Annuity Under the General Formula (PDF) — §50A2.1 gives the average salary rule, the 3-year window, and the weighting of each rate by time held.
• 5 U.S.C. § 8401(3) — the statutory definition of “average pay” the handbook restates: the largest annual rate from averaging basic pay over any 3 consecutive years.
• 5 U.S.C. § 8331(3) — what basic pay is, and the exclusions for overtime, bonuses, allowances, and awards.
• OPM CSRS/FERS Handbook, Chapter 51 — Creditable Service (PDF) — the 360-day service year, and which periods count toward the 3 consecutive years.

Last reviewed: August 2026