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Your Federal Employees Retirement System (FERS) supplement equals your Social Security estimate at age 62, multiplied by your years of FERS civilian service, divided by 40. The FERS supplement calculator above runs that formula and then applies the 2026 earnings test. The earnings test cuts the supplement $1 for every $2 you earn from work above $24,480. The result is a monthly figure paid until you turn 62, when the supplement stops.
How the FERS Supplement Is Calculated
The FERS supplement is your Social Security benefit at 62 multiplied by a fraction: your total years of service over 40. The formula comes from 5 U.S.C. 8421. The Social Security figure it uses is the benefit based on your federal civilian service earnings.
The calculator asks for three numbers:
- Social Security estimate at age 62 (monthly): defaults to $1,800.
- Years of FERS civilian service: defaults to 30.
- Earnings from work while on the supplement (per year): defaults to $0.
The statute rounds your service to the nearest whole year, with one-half rounding up, and the calculator does the same. Service of 29 years and 6 months counts as 30. Service of 29 years and 5 months counts as 29. The top of the fraction cannot go above 40, so 42 years of service counts the same as 40 and pays the full $1,800 estimate.
With the default inputs, the math is $1,800 x 30 / 40 = $1,350 a month. That number appears as Full Supplement. With $0 in earnings, Earnings-Test Reduction shows $0, and Supplement You Keep shows the full $1,350. The line-by-line breakdown shows each step. The Copy result button lets you paste the figures into your own notes.
Treat the result as a planning estimate. The Office of Personnel Management (OPM) computes your real supplement from your Social Security earnings record.
How Working After Retirement Cuts the Supplement
Working after retirement reduces the supplement by 50 percent of your yearly earnings above the Social Security exempt amount, which is $24,480 for 2026. The rule is in 5 U.S.C. 8421a, and the exempt amount follows Social Security's retirement earnings test. The Social Security Administration (SSA) lists the 2026 figure of $24,480, up from $23,400 in 2025, on its exempt amounts page.
Add a job paying $40,000 a year to the default inputs:
- Earnings above the exempt amount: $40,000 - $24,480 = $15,520.
- Yearly reduction: $15,520 x 50% = $7,760.
- Monthly reduction: $7,760 / 12 = about $647.
- Supplement you keep: $1,350 - $647 = about $703 a month.
The reduction is spread evenly across 12 months, and it cannot exceed the supplement you were owed for that year. At $1,350 a month, a full year of supplement is $16,200. Reaching a $16,200 reduction takes $32,400 of earnings above the exempt amount. At the 2026 exempt amount, earnings of $56,880 or more remove the whole supplement for the year.
The reduction starts months after you earn the money. A year's earnings reduce the 12 monthly payments that begin on the first day of the seventh month after that year ends. Earnings from 2026 reduce your payments from July 2027 to June 2028.
Only earnings from periods when you were entitled to the supplement count. Pay you earned before your supplement started does not enter the test.
Special-category retirees get an exception. Some people retire under the provisions in 5 U.S.C. 8412(d)(1) or (e), or 8414(c). That group covers law enforcement officers, firefighters, air traffic controllers and others. For them, earnings before minimum retirement age do not count. Tick the box labeled "Special category (law enforcement, firefighter, air traffic controller) and still under my minimum retirement age," and the calculator skips the earnings test. Untick it for years after you pass your minimum retirement age, because your earnings count from that point.
Three changes move your answer:
- A different Social Security estimate changes the full supplement.
- More years of service also change the full supplement.
- A new exempt amount changes the earnings test.
The calculator uses the 2026 amount. Rerun your numbers once SSA posts the 2027 figure on its exempt amounts page.
Who Does Not Get the Supplement
FERS retirees who take a deferred annuity, and FERS retirees who retire on disability, get no supplement. If you fall in either group, skip this calculator. Use the FERS annuity calculator to estimate your basic annuity instead. Read the FERS supplement explained for the full eligibility rules.
If you do qualify, run the FERS annuity calculator too, because it computes your basic annuity and leaves the supplement out. If you plan to draw on your Thrift Savings Plan (TSP) before 62, model those draws with the TSP withdrawal calculator.
Frequently Asked Questions
How to calculate the FERS supplement?
Multiply your Social Security estimate at 62 by your years of FERS civilian service, then divide by 40. Round your service to the nearest whole year, with one-half rounding up, and cap it at 40. A $1,800 estimate with 30 years gives $1,350 a month before any earnings reduction.
What is the income limit for the FERS supplement?
The 2026 limit is $24,480 a year in earnings from work. Above that, the supplement drops $1 for every $2 you earn, and the cut starts in July of the following year. Special-category retirees who are still under their minimum retirement age are exempt from the test.
Does a pension or TSP withdrawal count as earnings for the FERS supplement?
The earnings test counts earnings from work, measured under Social Security's retirement earnings test. Under 5 U.S.C. 8421a, the test uses Social Security's exempt amount. SSA lists the yearly limits on its exempt amounts page. For a pension or a TSP withdrawal in your own case, ask OPM Retirement Services.
Where do I find my Social Security estimate at 62?
Your estimate at 62 is on your Social Security statement in my Social Security. Sign in, find the monthly benefit for age 62, and type it into the "Social Security estimate at age 62 (monthly)" field above. Then enter your years of FERS service to see your full supplement and the amount you keep.