How This Calculator Works

The FERS Pension Calculator estimates your Federal Employees Retirement System basic benefit using the standard OPM computation formula. It also estimates the FERS Special Retirement Supplement (if eligible), projects COLA-adjusted pension values for 10 years, and shows the impact of working additional years.

The High-3 Formula

The core computation is:

FERS Basic Benefit = High-3 Average Salary × Years of Service × Multiplier

Multiplier rules:
  If retirement age ≥ 62 AND years of service ≥ 20:
    Multiplier = 1.1%
  Otherwise:
    Multiplier = 1.0%

Annual Pension = High-3 × Years × Multiplier
Monthly Pension = Annual Pension / 12

The High-3 average salary is the average of your highest three consecutive years of basic pay (base salary + locality pay). This calculator uses a single input for the High-3 rather than computing it from pay history. For most employees, the High-3 is the last three years of service.

Multiplier Rules

The multiplier determines how much each year of service is worth. The standard multiplier is 1.0% — meaning each year of service earns you 1% of your High-3 salary as annual pension income.

The enhanced 1.1% multiplier applies only when both conditions are met: you are age 62 or older at separation, and you have 20 or more years of creditable service. If either condition is not met, the 1.0% multiplier applies to all years.

This is an all-or-nothing threshold — the 1.1% applies to every year of service if you qualify, not just years after age 62 or the 20th year.

FERS Supplement Approximation

The FERS Special Retirement Supplement (SRS) bridges the gap between retirement and age 62. This calculator approximates it using the standard ratio method:

FERS Supplement ≈ Estimated SS Benefit at 62 × (FERS Service Years / 40)

Supplement Duration = max(62 - Retirement Age, 0) years

If retirement age ≥ 62: Supplement = $0 (not applicable)

The actual OPM calculation uses Social Security Administration earnings records and is more precise. This approximation provides a reasonable estimate for planning purposes. The supplement ratio is capped at 1.0 (40+ years of FERS service).

The supplement is only available for certain retirement types: MRA+30, age 60+20, or involuntary/early retirement. Involuntary and early retirees get it only once they reach their MRA. It is not available under MRA+10, deferred retirement, or disability retirement. This calculator does not validate eligibility — it estimates the amount if eligible.

COLA Calculation

FERS cost-of-living adjustments follow specific rules based on the Consumer Price Index:

If CPI increase > 3%:
  COLA = CPI - 1 percentage point

If CPI increase is 2% to 3% (inclusive):
  COLA = 2%

If CPI increase < 2%:
  COLA = full CPI increase

Adjusted Pension (Year N) = Previous Year Pension × (1 + COLA)

The calculator projects 10 years of COLA-adjusted pension values using the user's assumed CPI rate. In reality, CPI varies each year — the projection assumes a constant rate for illustration.

Important: regular FERS retirees get no COLA until they reach 62 (5 U.S.C. §8462(c)(3)). The projection follows that rule: in any year before you reach 62 your pension stays flat, and the COLAs you missed are not added back later. Special-provision retirees (law enforcement, firefighters, air traffic controllers) and disability retirees do get COLAs before 62; this calculator models a regular FERS retirement.

Comparison Table

The "work longer" comparison shows the pension impact of +1, +2, and +3 additional years of service. Each scenario recalculates the multiplier based on the new age and years of service. This is particularly valuable for employees near the 62/20 threshold where the multiplier jumps from 1.0% to 1.1%.

Each row shows two starts, because the law lets you choose when the pension begins. "Start right away" takes it the day you leave, with the MRA+10 reduction if you are under 62 with fewer than 30 years. "Start with no cut" takes it at the earliest age with no reduction: 62 with 5 or more years, 60 with 20 or more, or the MRA with 30 (5 U.S.C. 8412(g)(2) lets an MRA+10 retiree postpone the start; 8413(b) and 8415(h)(2) set the deferred start). The monthly gain compares the no-cut starts, so working longer is never shown as lowering your pension. Which start is better for you also depends on how long you expect to draw it, which the calculator does not weigh.

The comparison assumes the High-3 salary remains constant. In practice, continued employment typically increases the High-3, making the actual benefit of extra years slightly larger than shown.

MRA Table

The FERS Minimum Retirement Age depends on birth year and ranges from 55 to 57: 55 if born before 1948, rising 2 months a year to 56 for 1953-1964, then 2 months a year to 57 for 1970 and later (5 U.S.C. 8412(h); OPM). The calculator works out your birth year from your current age, so it can be a year out near a birthday.

It then applies the retirement rules (5 U.S.C. 8412, 8415(f); OPM): an unreduced annuity at 62 with 5 years, 60 with 20, or the MRA with 30; an MRA+10 annuity, at the MRA with 10 to 29 years, reduced 5% for each year under 62 (5/12 of 1% a month), permanently, unless it starts at 60 with 20 or more years; and, before the MRA, no immediate annuity but a deferred one (5 U.S.C. 8413), payable unreduced at 62 with 5 or more years, at 60 with 20 or more years, or at the MRA with 30 years (8415(h)(2) lifts the reduction when the age-and-service test of 8412(a) or (b) is met on the start date). With 10 or more years, a deferred annuity may also start on any date from the MRA to 62 (8413(b)(1)), reduced 5/12 of 1% for each full month before 62 (8415(h)(1)). Fewer than 5 years gives no annuity.

Data Sources

OPM FERS Handbook — Authoritative guide for FERS computation rules, eligibility, COLAs, survivor benefits, and the Special Retirement Supplement. Published by the Office of Personnel Management.
5 USC Chapter 84 — Federal statute establishing FERS, including benefit computation (§8415), COLAs (§8462), and the Special Retirement Supplement (§8421).
Social Security Administration (SSA) — Used for estimated Social Security benefit at age 62, which feeds the FERS Supplement calculation.
Bureau of Labor Statistics (BLS) — CPI data used for historical COLA context and default assumption calibration.

Limitations

Does not model disability, early-out (VERA), involuntary or special-category retirement.
The headline figure assumes the pension starts when you leave, or at the first no-cut age if you leave before you can draw it. Postponing an MRA+10 start to a date between the two is allowed but only the two ends are shown (the no-cut start, and for a deferred leaver the earliest start).
Does not account for CSRS-offset or CSRS-transferee computation differences.
Does not model unused sick leave credit toward additional service months.
FERS Supplement eligibility is not validated — calculator estimates the amount regardless of retirement type.
COLA is modelled from age 62 for regular FERS retirees who retire younger (as described above); it does not model special-provision retirees, who receive COLAs earlier.
Assumes constant CPI — real inflation varies annually.
Does not model survivor benefit reductions (10% for full, 5% for partial).
Does not account for military service deposit requirements or deposit refund impacts.
High-3 is a single input — does not compute from actual pay history or project future raises.

Last Updated

April 2026 — Initial release. Formula based on current OPM FERS handbook and 5 USC Chapter 84. COLA rules current as of the most recent annual adjustment.

October 2026 — Corrected the COLA band for CPI rises between 2% and 3%: FERS pays 2% in that band (5 U.S.C. §8462(b); OPM CSRS/FERS Handbook ch. 2), not the full CPI rise the calculator previously applied, which overstated projected pensions. Pay-cap figures on the calculator page updated to OPM's 2026 salary tables (GS-15/10 $164,301; EX-IV cap $197,200; SES maximum $228,000 / $209,600).

FERS Pension Calculator — Methodology