Federal employees under the Federal Employees Retirement System (FERS) have a three-legged retirement stool: the FERS basic annuity (pension), the Thrift Savings Plan (TSP), and Social Security. The pension component alone involves a formula that most federal employees do not calculate until they are a few years from retirement. Knowing it early changes contribution decisions.
The FERS annuity formula
The basic annuity is:
Under 62 or 62+ with less than 20 years: 1% x High-3 average salary x Years of creditable service
62 or older with 20+ years: 1.1% x High-3 average salary x Years of creditable service
The "High-3" is the average of your highest three consecutive years of basic pay. For most employees, this is their last three years before retirement.
Example: You retire at 60 with 30 years of service. Your High-3 average salary is $120,000.
Annuity = 1% x $120,000 x 30 = $36,000 per year = $3,000 per month
If you wait until 62 with those same 30 years:
Annuity = 1.1% x $120,000 x 30 = $39,600 per year = $3,300 per month
That extra 0.1% per year multiplied by 30 years adds $3,600 annually for the rest of your life.
Minimum Retirement Age (MRA)
You cannot just decide to retire whenever you want and collect a FERS pension. The Minimum Retirement Age depends on your birth year:
- Born before 1948: MRA = 55
- Born 1948-1952: MRA = 55 + 2 months for each year after 1948
- Born 1953-1964: MRA = 56
- Born 1965-1969: MRA = 56 + 2 months for each year after 1965
- Born 1970 or later: MRA = 57
The combinations:
- MRA + 30 years: Full, unreduced annuity
- MRA + 10 years: Reduced annuity (5% reduction per year under 62)
- 60 + 20 years: Full, unreduced annuity
- 62 + 5 years: Full annuity at the 1.1% rate
The FERS Supplement
If you retire before 62 on an immediate annuity (MRA+30 or 60+20), you receive a FERS supplement that approximates the Social Security benefit you have earned as of your retirement date. This supplement stops when you turn 62 and become eligible for actual Social Security.
The supplement is calculated as: (Years of FERS service / 40) x Social Security benefit estimate at 62
If your estimated Social Security benefit at 62 is $2,200/month and you have 30 years of FERS service:
Supplement = (30/40) x $2,200 = $1,650/month
This supplement is subject to the Social Security earnings test if you work after retirement.
The TSP component
The Thrift Savings Plan is the federal equivalent of a 401k. The agency automatically contributes 1% of pay and matches up to an additional 4% (5% total agency contribution if you contribute 5%).
At a $120,000 salary contributing 5%:
- Your contribution: $6,000/year
- Agency match: $6,000/year (1% automatic + 4% match)
- Total: $12,000/year
Over 30 years at 7% average return:
Approximately $1,135,000 in the TSP
At a 4% withdrawal rate, that supports $45,400/year in retirement income, on top of the $36,000-$39,600 pension and Social Security.
Cost of Living Adjustments (COLA)
FERS annuities receive annual COLA adjustments, but they are less generous than Social Security COLAs:
- If CPI increase is under 2%: full COLA
- If CPI increase is 2-3%: 2%
- If CPI increase is over 3%: CPI minus 1%
Over a 25-year retirement, this means your FERS pension gradually loses purchasing power relative to inflation. The TSP and Social Security partially compensate.
Running the projection
The FERS retirement calculation involves your High-3, years of service, retirement age, TSP balance, and Social Security estimate. I built a FERS retirement calculator that models all three components together and shows your projected total retirement income under different retirement timing scenarios.
I'm Michael Lip. I build free developer tools at zovo.one. 500+ tools, all private, all free.
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