FERS Retirement Formula: High-3, Service, and Reductions

The FERS retirement formula is straightforward on its face: your high-3 average salary multiplied by your years of creditable service multiplied by 1%. That multiplier rises to 1.1% if you retire at age 62 or later with at least 20 years of service. Everything else in a FERS pension calculation, from sick leave conversion to survivor reductions, is about getting the two main inputs right and then adjusting the result.

Annual Annuity = High-3 Average Salary × Years of Service × 1% (or 1.1%)

An employee with a high-3 of $100,000 and 30 years of service retiring at age 60 gets $100,000 × 30 × 0.01 = $30,000 per year, or $2,500 per month before deductions. The same employee retiring at 62 with the same service gets $100,000 × 30 × 0.011 = $33,000 per year, an extra $250 every month for life.¹

What Counts as Your High-3 Average Salary

The high-3 is the highest basic pay you earned over any 36 consecutive months of service. Those 36 months are usually the final three years of a career because pay tends to peak near the end, but the window can land anywhere your salary was highest.²

Basic pay includes your General Schedule or equivalent rate plus locality pay adjustments. Shift differentials (also called shift rates) count as well, since retirement deductions are withheld on them. What does not count: overtime, bonuses, lump-sum payouts for unused annual leave, and allowances for travel or uniforms. If you worked night shifts and assumed that differential was boosting your high-3, it depends on whether it qualifies as a shift rate under your pay system rather than premium pay.²

You can verify your salary history through Leave and Earnings Statements or annual personal benefits statements. Getting this number right matters more than anything else in the formula. A $1,000 error in the high-3 translates directly into a $10 to $11 difference in every monthly check for life.

How Creditable Service Is Counted

Your total creditable service counts all years and full months of civilian federal employment during which you contributed to the FERS retirement fund. Days left over after totaling full years and months are dropped, so 25 years, 10 months, and 28 days becomes 25 years and 10 months.

Unused Sick Leave

Unused sick leave at retirement gets converted into additional service time for the annuity calculation. For anyone retiring on or after January 1, 2014, 100% of the sick leave balance is credited.³ The conversion uses a 2,087-hour work year, so that many hours of unused sick leave adds a full year to your service total.⁴ Sick leave credit cannot be used to meet the minimum service requirements for retirement eligibility. It only boosts the annuity computation after you already qualify.¹

Military Service Buy-Back

If you served in the military before your federal civilian career, that time can count toward your FERS annuity, but only if you make a deposit. For most service periods, the deposit is 3% of your military basic pay. Interest begins accruing if the deposit is not paid in full within three years of the date it becomes payable.⁵ Complete the deposit before you retire. Skipping it means that military time may not count in your annuity calculation, and could also affect how your Social Security benefit interacts with FERS.

Part-Time Service

If you worked part-time during any portion of your career, that period is prorated. OPM compares the hours you actually worked against the full-time hours available for the same period and produces a proration factor. Your annuity for those years is then reduced proportionally. If you worked 20 hours per week for five years in a position with a 40-hour full-time schedule, those five years count as roughly 2.5 years in the formula. The proration only affects the part-time period. Any full-time years are calculated at their full value.

Different Multipliers for Special Groups

Several federal occupations use a more generous formula because the work is physically demanding and careers tend to be shorter. Employees in law enforcement, firefighting, and air traffic control, along with nuclear materials couriers, Capitol Police, Supreme Court Police, and Customs and Border Protection officers, receive a 1.7% multiplier for the first 20 years of service. Any years beyond 20 revert to the standard 1% rate.²

A law enforcement officer retiring at 50 after 25 years with a $100,000 high-3 would calculate the annuity in two pieces. The first 20 years: $100,000 × 20 × 0.017 = $34,000. The remaining 5 years: $100,000 × 5 × 0.01 = $5,000. Total: $39,000 per year. Compare that to $25,000 under the standard civilian formula for the same salary and service, a 56% increase.⁶

Members of Congress and certain congressional staff also qualify for the 1.7% multiplier on up to 20 years of congressional or Member service, provided they have at least 5 years in those roles. Service beyond 20 years in congressional positions reverts to 1%, and any non-congressional federal service is always calculated at the standard rate.¹

The MRA+10 Early Retirement Reduction

If you retire at your Minimum Retirement Age with at least 10 years of service but fewer than 30, you take a permanent cut to the number the formula produces. The reduction is 5% for each full year you are under age 62 at the time your annuity begins, calculated as five-twelfths of 1% for each month you fall short of 62.¹

Retiring at 57 under MRA+10 means you are five years short of 62, a 25% permanent reduction. On a $20,000 gross annuity, that is $5,000 per year gone forever. The reduction does not go away when you eventually turn 62. You can avoid it by postponing the start of your annuity payments until you reach 62, but that means living without the pension in the interim.⁷

Reductions That Come Out of the Gross Annuity

The number the formula produces is a gross figure. Several deductions will reduce what actually lands in your bank account each month.

Survivor Benefit Election

If you are married, FERS automatically provides a full survivor annuity to your spouse unless both of you elect otherwise. Choosing the full survivor benefit, which pays your surviving spouse 50% of your unreduced annuity for life, permanently reduces your annuity by 10%. A partial survivor election, providing 25% to your spouse, reduces it by 5%.⁸ You can elect no survivor benefit, but your spouse must consent in writing. This is a permanent, irrevocable decision. You cannot change it after retirement.

Federal and State Income Taxes

Your FERS annuity is largely taxable as ordinary income. A small portion of each payment is treated as a tax-free return of the retirement contributions you made during your career, but the bulk of the annuity is subject to federal income tax.⁹ State income tax treatment varies. Some states fully exempt pension income, others tax it like any other income. Check your state’s rules before building a retirement budget.

Health and Life Insurance Premiums

If you continue Federal Employees Health Benefits (FEHB) coverage into retirement, premiums are deducted from your annuity. The same applies to Federal Employees’ Group Life Insurance (FEGLI) if you maintain coverage beyond the free basic amount. These costs can take a noticeable bite, especially for family-level health coverage.

A Full Worked Example

Layering each component is what turns the formula into a realistic estimate. Here is the calculation for a GS-13 employee born in 1966 with an MRA of 56 and 4 months:

High-3 average salary: $115,000
Years of creditable service: 30 years, plus 6 months of sick leave credit = 30.5 years
Retirement age: 57 (MRA with 30+ years, so no early retirement reduction)
Multiplier: 1% (under age 62)
Gross annuity: $115,000 × 30.5 × 0.01 = $35,075 per year
Survivor benefit reduction (full): $35,075 × 0.10 = −$3,508
Net annuity before taxes: approximately $31,567 per year, or about $2,631 per month

That annuity alone replaces roughly 27% of the employee’s working salary, which is by design. FERS was built as one leg of a three-part system alongside Social Security and the Thrift Savings Plan. Relying on the annuity alone, without a healthy TSP balance, leaves most retirees well short of their pre-retirement income.

1
Office of the Law Revision Counsel. 5 USC 8415 – Computation of Basic Annuity
2
U.S. Office of Personnel Management. FERS Information – Computation
3
U.S. Office of Personnel Management. Fact Sheet – Sick Leave General Information
4
U.S. Office of Personnel Management. Retirement Facts 8
5
U.S. Office of Personnel Management. Service Credit
6
Office of Personnel Management. Information for FERS Annuitants
7
U.S. Office of Personnel Management. What Is a Minimum Retirement Age (MRA) Plus 10 Annuity Under FERS
8
U.S. Office of Personnel Management. How Is the Reduction Calculated
9
U.S. Office of Personnel Management. Learn More About Taxes and Federal Retirement