The core formula
For most regular FERS employees, the annual basic annuity is calculated as high-3 average salary multiplied by years of creditable service multiplied by the FERS multiplier. The result is the gross annual pension before survivor election reductions, taxes, health premiums, and other deductions.
This formula is simple, but each input has rules. High-3 is not always final salary. Years of service may include deposits or exclude some periods. The multiplier changes only when specific age and service conditions are met.
High-3 salary
High-3 is the average of your highest 36 consecutive months of basic pay, generally including locality pay. Overtime, bonuses, awards, and travel reimbursements generally do not count. For employees with steadily rising pay, the high-3 is usually the final three years. For employees who move to part-time work, take a downgrade, or move to a lower locality late in the career, the best 36-month period may be earlier.
Read the detailed high-3 guide →
Years of service
Years of service is the career-length multiplier. One more year generally adds 1.0% of high-3 to annual pension, or 1.1% if the enhanced multiplier applies. Creditable service can include civilian federal service and military service with a completed deposit. Unused sick leave may increase the computation after eligibility is established.
Read the detailed years of service guide →
1.0% vs. 1.1%
The standard multiplier is 1.0%. The 1.1% multiplier generally applies if you retire at age 62 or later with at least 20 years of service. This is a 10% increase to the multiplier and applies across the service years in the formula. Retiring at MRA+30 before 62 can be unreduced, but it usually still uses 1.0%.
Worked examples
| High-3 | YOS | Multiplier | Annual pension |
|---|---|---|---|
| $100,000 | 20 | 1.0% | $20,000 |
| $150,000 | 30 | 1.0% | $45,000 |
| $150,000 | 30 | 1.1% | $49,500 |
| $180,000 | 35 | 1.1% | $69,300 |
These are gross pension amounts. A survivor election can reduce the retiree's monthly benefit by 5% or 10%. FEHB premiums, federal tax, and state tax can reduce take-home income further.
What the formula does not include
The basic pension formula does not include TSP, Social Security, the FERS Annuity Supplement, taxes, FEHB subsidy value, or survivor risk. Those items matter for retirement readiness, but they are separate from the statutory basic annuity calculation.
Use this formula as the foundation, then model full retirement income with pension, TSP, and Social Security together.
Monthly pension estimate
OPM pays the FERS annuity monthly, so many employees want to convert the annual result into a monthly amount. Divide the annual pension by 12, then account for deductions. A $48,000 annual gross pension is $4,000 per month before survivor election, federal tax withholding, state tax where applicable, FEHB premiums, FEDVIP premiums, and other elected deductions. The gross formula is useful for comparing retirement dates, but take-home pension requires a second layer of cash-flow planning.
Survivor election is usually the largest pension-specific reduction. A maximum survivor election can reduce the retiree's pension by 10%, while a partial election can reduce it by 5%. That reduction is applied before many retirees think about taxes or healthcare, so a $4,000 monthly gross pension might become $3,600 before tax if the maximum survivor option is elected.
COLA and purchasing power
FERS pensions can receive cost-of-living adjustments, but COLA rules are not identical to CSRS and do not always fully match inflation. Many regular FERS retirees do not receive COLA until age 62, and the FERS COLA formula can lag CPI when inflation is above certain levels. This means the first-year pension amount is only part of the story. The inflation path during retirement affects long-term purchasing power.
When comparing two retirement dates, look at both starting pension and timing. Retiring earlier may start payments sooner, but waiting can increase high-3, service years, and potentially multiplier. Retiring later may also reduce the number of years pension is paid. Present value analysis helps compare those trade-offs more clearly than a first-year pension number alone.