Compare the FERS three-leg stool (pension + TSP + Social Security) against the CSRS single-pension model. Side-by-side math on identical salaries to see which produces more retirement income.
CSRS (Civil Service Retirement System) was the federal pension system from 1920 through 1986. FERS (Federal Employees Retirement System) replaced it for new hires starting 1/1/1987. A few CSRS and CSRS-Offset employees are still working, and the comparison still matters when modeling reciprocity, buybacks, or just understanding what different colleagues face at retirement.
The core difference: CSRS is a defined-benefit-only system — your pension is the whole retirement plan. FERS is a three-leg stool: a smaller defined-benefit pension, plus TSP (with match), plus Social Security. Both can produce comparable retirement income, but the math is very different.
CSRS pension formula: 1.5% of high-3 for first 5 years + 1.75% for next 5 years + 2% per year thereafter. At 30 years of service, that's 56.25% of high-3. At 40 years, 76.25%. CSRS employees pay 7% of salary toward this and do NOT pay into Social Security on federal wages.
FERS pension formula: 1% of high-3 per year of service (1.1% if you retire at 62+ with 20+ years). At 30 years and retirement before 62, that's 30% of high-3 — much smaller. But FERS employees ALSO get TSP matching (1% automatic + up to 4% match = 5% max), pay into Social Security on full federal wages, and qualify for the FERS Annuity Supplement if they retire before 62.
This tool runs both. Enter your years of service, high-3 salary, and retirement age — you get a true apples-to-apples comparison including the FERS Supplement, projected TSP balance with 5% match captured, and Social Security at full retirement age.
Step 1 — Pick your scenario. Most likely you're FERS (or BRS for military). If you started federal service before 1984 you're CSRS. If you transferred from CSRS to FERS in the open seasons, you may be CSRS-Offset — covered here too.
Step 2 — Enter common inputs. Years of federal service at retirement, high-3 salary, and retirement age. The tool uses the same inputs for both systems so the output is directly comparable.
Step 3 — Compare the totals. The output table shows the CSRS-only monthly check, the FERS pension + TSP withdrawal (at 4% safe rate on your projected balance) + Social Security at full retirement age. For most career-long employees, the totals come within 10–20% of each other; the answer to "which is better" depends heavily on TSP returns and Social Security timing.
Enter years of service, high-3 salary, and retirement age. The tool runs the CSRS formula (richer pension, no SS), the FERS formula (smaller pension + TSP + SS), and shows the apples-to-apples total monthly income.
Open the comparison tool →No — CSRS has been closed to new hires since 12/31/1986. Anyone who started federal service on or after 1/1/1987 is on FERS. There are still tens of thousands of CSRS retirees and a few thousand active CSRS workers (very long-tenured) but no new entry.
CSRS-Offset is a hybrid for employees who left federal service after 1984 and returned with at least 5 years of CSRS service: they remain on CSRS but ALSO pay into Social Security on federal wages. At retirement, their CSRS pension is reduced ('offset') by the amount of Social Security benefit attributable to their CSRS-Offset service. Practically, the total of pension + SS = roughly what straight CSRS would have paid.
If you retire from FERS before age 62 with at least 20 years of service, the FERS Supplement pays you an approximation of your future Social Security benefit until age 62. It's based on your FERS years and your projected SS benefit. The Supplement ends at 62 and is reduced if you have earned income exceeding the Social Security annual earnings limit. Special-category employees (LEOs, ATCs, firefighters) get the Supplement even when retiring at the minimum age, with no earnings test until age 62.
FERS uses a 1% multiplier (1.1% at age 62 with 20+ years) per year of service. CSRS uses a 1.5–2% multiplier. At 30 years of service, FERS gives 30% of high-3 vs. CSRS giving ~56%. But FERS adds TSP matching (which CSRS doesn't have) and Social Security (which CSRS opted out of). The smaller pension is intentional — it's one leg of three instead of the whole stool.
CSRS COLA is based on CPI-W, paid every January, with no minimum age requirement. FERS COLA is partial CPI (1% less than CPI for inflation between 2% and 3%, 2% for any year with CPI ≥ 3%, full CPI when CPI < 2%) and generally doesn't begin until age 62 unless you're a special category employee.