FERS — the Federal Employees Retirement System — is a three-layer system: a basic annuity (what this page estimates), Social Security, and the Thrift Savings Plan. The annuity layer is a defined benefit: a formula, not a guess. OPM publishes it plainly — high-3 average salary × multiplier × years of creditable service — and that is exactly, and only, what this calculator computes.
Know what this is not: an official estimate. This page is an educational simplification of the published formula. It does not replace your agency’s HR office, your SF-50 record, or an official OPM benefits estimate — which also account for survivor elections, unused sick leave conversion, deposits, and early-retirement reductions. For decisions, go to OPM and your HR.
How the FERS formula works
Step 1 — find your high-3. Average your basic pay over your highest-paid 36 consecutive months — for most federal employees, that is the final three years of their career. Basic pay excludes overtime and most bonuses.
Step 2 — pick the multiplier. The standard multiplier is 1.0% of high-3 per year of service. Retire at age 62 or later and with 20 or more years of creditable service, and OPM raises it to 1.1% — a permanent 10% raise on the annuity for waiting. The calculator applies this automatically from the age you enter and shows which rate was used.
Step 3 — multiply by service. Years of creditable FERS service (including converted unused sick leave at retirement) complete the formula. The result is your gross annuity before any survivor-election reduction, taxes, or offsets.
FERS annuity = high-3 average salary × multiplier × years of service
multiplier = 1.1% if (age ≥ 62 and years ≥ 20), else 1.0%The 62/20 breakpoint is worth real money. On the sample below, waiting from 61 to 62 lifts the multiplier from 1.0% to 1.1% — worth roughly two thousand dollars a year, every year, for life. Whether waiting is right depends on your full picture: Social Security timing, TSP balances, and health. This page isolates the annuity layer so you can see its arithmetic clearly.
The sample, end to end. Your high-3 is $98,000 with 22 years of creditable service. Retire at 62 and the 1.1% multiplier applies: $98,000 × 1.1% × 22 = $23,716 a year (about $1,976 a month). Retire at 61 instead and the rate drops to 1.0%: $21,560 a year — waiting one year is worth $2,156 annually, for life. Same salary, same service; the age you file is the whole difference.
Terms & definitions
High-3
The average of your highest 3 consecutive years of basic pay — almost always your final 36 months. The salary base of the FERS formula.
Creditable service
Federal service that counts toward the annuity calculation, including converted unused sick leave at retirement.
FERS annuity
The defined-benefit pension paid for life under FERS: high-3 × multiplier × years of service.
Minimum Retirement Age (MRA)
The earliest age at which you can retire with an immediate annuity under FERS rules — 55 to 57 depending on birth year.
Frequently asked questions
Does this calculator replace my official OPM estimate?
No — and it is not trying to. It applies the published FERS annuity formula to three numbers you provide. An official estimate from your agency or OPM also accounts for survivor benefit elections, unused sick leave conversion, military deposits, part-time proration, and any early-retirement reduction. Use this page to understand the formula; use OPM and your HR office for the number that matters.
When do I get the 1.1% multiplier instead of 1%?
Only when you retire at age 62 or later and have at least 20 years of creditable service. Both conditions must hold at your separation date — the calculator checks them from the age you enter and shows the rate it used. Retire at 62 with 19 years, or 61 with 25 years, and the multiplier stays 1.0%.
What is the FERS Special Retirement Supplement?
A bridge payment for certain retirees — typically those who reach their Minimum Retirement Age with 30 years of service, or age 60 with 20 years — paid from retirement until age 62, when Social Security can begin. It approximates what your Social Security benefit would be from federal service. It is not part of the basic annuity formula, so this calculator does not estimate it; OPM’s published rules govern eligibility and amounts.
How does FERS fit with Social Security and my TSP?
FERS is deliberately three layers. Layer 1 is the basic annuity you estimated here. Layer 2 is Social Security — as a FERS employee you pay into it, so no pension offset applies (unlike some CSRS retirees). Layer 3 is the Thrift Savings Plan, your defined-contribution account with agency matching. A complete retirement plan coordinates all three — this page isolates layer 1 so its math stays visible.
References
- OPM — FERS Information (official annuity rules and eligibility): opm.gov/retirement-services/fers-information/
- OPM — CSRS and FERS Handbook (retirement computation chapters): opm.gov/retirement-services/publications-forms/csrs-fers-handbook/
- SSA — Retirement benefits (the Social Security layer of FERS): ssa.gov/benefits/retirement/