The FERS retirement formula calculates your federal pension as 1% of your high-3 average salary multiplied by your years of creditable service — or 1.1% if you retire at age 62 or older with at least 20 years of service. This single formula determines your annuity for life. Here's how to apply it correctly and what most federal employees get wrong.
What Is FERS and How Does the Annuity Work?
The Federal Employees Retirement System (FERS) is the primary retirement program for federal employees hired after 1983. It has three components:
- FERS Basic Annuity — the defined pension calculated by the formula
- Thrift Savings Plan (TSP) — the 401(k)-style account with agency matching
- Social Security — federal employees pay full Social Security taxes and earn full benefits
Most retirement planning for federal employees focuses on the annuity because it's the guaranteed income floor. TSP and Social Security add on top.
The FERS Annuity Formula
The formula is straightforward, but the inputs take work to calculate correctly.
Standard formula (under age 62, or 62+ with fewer than 20 years):
1% × High-3 Average Salary × Years of Creditable Service
Enhanced formula (age 62+ with 20+ years):
1.1% × High-3 Average Salary × Years of Creditable Service
The 0.1% difference sounds small. On a $90,000 high-3 with 30 years of service, it's the difference between $27,000 and $29,700 per year — $2,700 annually, for life. That's why the 62+20 threshold matters.
What Is the "High-3 Average Salary"?
Your high-3 is the average of your highest 36 consecutive months of base pay. For most employees approaching retirement, that's typically the final three years — but not always.
What counts toward high-3:
- Basic pay (your regular salary)
- Locality pay (included since 1994)
- Retained pay
What does NOT count:
- Overtime
- Bonuses
- Awards
- Allowances
- Night differential (generally)
If you had a significant promotion or locality adjustment in the last 3 years, your high-3 is straightforward. If your pay has been flat or you moved to a lower-pay position temporarily, you may need to look back further to find your actual highest 36 consecutive months.
What Counts as "Creditable Service"?
This is where most estimates go wrong. Creditable service is not simply years employed by the federal government. You need to count carefully.
Included in FERS creditable service:
- Years in a FERS-covered position
- Military service (if you paid the deposit)
- CSRS-covered time (if you transferred to FERS)
- Sick leave (converted at retirement — every 174 hours = 1 month)
Not automatically included:
- Military service where you did NOT pay the deposit
- Temporary federal employment before age 18
- Periods of LWOP exceeding 6 months in a calendar year
The sick leave conversion is often overlooked. If you retire with 2,000 hours of unused sick leave, that converts to approximately 11.5 months of additional creditable service — adding nearly a full year to your annuity calculation.
Real Examples: FERS Annuity Estimates
Here's what the formula looks like at different career points:
| High-3 Salary | Years of Service | Age at Retirement | Annual FERS Annuity |
|---|---|---|---|
| $75,000 | 20 years | 60 | $15,000 |
| $90,000 | 25 years | 57 | $22,500 |
| $100,000 | 30 years | 62 | $33,000 |
| $110,000 | 33 years | 62 | $39,930 |
| $85,000 | 28 years | 56 | $23,800 |
Note: The 62-with-30-years example uses the 1.1% multiplier. All others use 1%.
These are gross annuity figures before deductions. Your actual deposit will be reduced by:
- Survivor benefit election (up to 10% reduction for full survivor benefit)
- FEHB premiums (if you continue health coverage in retirement)
- Federal income tax withholding
- State income tax (varies by state)
The Minimum Retirement Age (MRA) Rules
You can't collect FERS at any age. The minimum depends on your birth year:
| Birth Year | Minimum Retirement Age |
|---|---|
| Before 1948 | 55 |
| 1948–1952 | 55–56 (graduated) |
| 1953–1964 | 56 |
| 1965–1969 | 56–57 (graduated) |
| 1970 or later | 57 |
Most federal employees born in 1970 or later have an MRA of 57. To retire at your MRA, you need 30 years of service. With 10–29 years, you can retire at MRA but your annuity is reduced 5% for each year under age 62 (unless you use the MRA+10 postponed option).
The FERS Special Retirement Supplement
If you retire before age 62 under an immediate, unreduced annuity, you may qualify for the Special Retirement Supplement (SRS) — a payment that bridges the gap until Social Security begins at 62.
The SRS approximates what Social Security would pay for your federal years of service. It's calculated by OPM and is subject to an earnings test (reduced if you have earned income over the annual limit).
The supplement is not indexed for inflation and stops at age 62 regardless of whether you claim Social Security. It's a meaningful income bridge for early FERS retirees — but it won't cover your full expected Social Security benefit.
Get Your Actual FERS Estimate
The formula gives you a solid ballpark. For a precise number — including sick leave conversion, survivor benefit impact, FEHB costs, and TSP modeling — use the FERS Annuity Estimator →.
The estimator walks you through every input, flags common calculation errors, and shows your take-home annuity after deductions. You can also run your complete federal retirement scenario — FERS annuity, TSP withdrawals, Social Security, and year-by-year projections — with the Federal RetireStack tool →.
Frequently Asked Questions
What is the FERS retirement formula? FERS calculates your annuity as 1% × your high-3 average salary × years of creditable service. If you retire at age 62 or older with at least 20 years of service, the multiplier increases to 1.1%, resulting in a 10% larger annuity.
How is the high-3 salary calculated for FERS? Your high-3 is the average of your highest 36 consecutive months of base pay (including locality pay). For most employees, this is the final three years of their career — but it's the highest 36 months, not necessarily the last 36 months.
Does unused sick leave count toward FERS retirement? Yes. At retirement, your unused sick leave is converted to additional creditable service at a rate of approximately 174 hours per month. An employee with 2,080 hours of sick leave would gain roughly 12 months of additional service credit, which can meaningfully increase the annuity calculation.
What is the FERS Special Retirement Supplement? The SRS is a payment for FERS employees who retire before age 62 under an unreduced annuity. It approximates the Social Security benefit earned during federal service and bridges the income gap from retirement to age 62. It is subject to an earnings test and ends at age 62 regardless of when you claim Social Security.
RetireStack provides retirement planning tools for federal employees. This article is for informational purposes only and does not constitute financial or benefits advice. Consult your agency HR office or a financial advisor for guidance specific to your situation.