FERS Pension Explained: How Your Federal Annuity Is Actually Calculated

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Your FERS pension comes down to one formula: High-3 average salary × years of creditable service × a multiplier of 1% (or 1.1%). FERS, the Federal Employees Retirement System, covers most federal employees first hired after December 31, 1983, with full FERS becoming effective January 1, 1987.

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According to the U.S. Office of Personnel Management (OPM), the federal agency that administers retirement benefits, the basic annuity for regular non-disability FERS retirements rests on three things: High-3 pay, creditable service, and the applicable multiplier. Once you know those three numbers, you can build a close estimate of your federal annuity.

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This guide from Federal Pension Advisors, a retirement planning firm that specializes in federal employee benefits, walks through each variable and the decisions that move it.

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How the FERS Pension Is Calculated: The Core Formula

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The FERS basic annuity uses one of two formulas, depending on your age and service at retirement. OPM's computation guidance sets the standard formula at 1% × High-3 average salary × years of creditable service.

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Retire at age 62 or older with at least 20 years of service, and the multiplier rises to 1.1%. That's a permanent 10% increase to your basic annuity calculation before reductions.

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That figure is your gross annuity, calculated before reductions, elections, taxes, and special-case adjustments. Three variables control the monthly income you'll receive for the rest of your life.

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Consider a federal employee with a $90,000 High-3, 30 years of service, who retires at age 62. She receives $29,700 per year before any reductions, per the formula OPM publishes. The same employee retiring one year earlier at 61 would use the 1% multiplier and receive $27,000. That's a $2,700 annual gap that lasts a lifetime.

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Each variable rewards specific decisions. Knowing which ones you can still influence before your retirement date is where real planning begins.

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Variable One: Your High-3 Average Salary

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Your High-3 is the average of your highest 36 consecutive months of basic pay. For most employees that's the final three years of service, but not always. OPM uses your highest-earning consecutive three-year window, whether or not it falls at the end of your career.

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Basic pay generally includes pay subject to retirement deductions, such as base salary and locality pay. According to OPM, it excludes overtime, bonuses, and awards.

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Some premium or differential pay depends on your employee category, so verify it on your SF-50 or with HR. Many employees overestimate their pension because they fold excluded amounts into their own math.

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Did you hold different pay rates during the 36-month window because of a promotion, step increase, or locality change? OPM weights each rate by the time you hold it, using a 360-day-year convention.

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One planning consequence matters here. Because your High-3 locks to your highest window, an early-career period at a high locality can sometimes outvalue your final years.

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If you relocated to a lower-locality area before retirement, an earlier window may produce a larger average. It's worth checking before you file.

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Variable Two: Years of Creditable Service

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Creditable service is the total time OPM counts toward your pension, and it includes more than your civilian years at the desk. According to OPM, creditable service can include civilian federal service, military service you've formally bought back through a deposit when eligible, and unused sick leave converted at retirement.

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The sick leave conversion is the detail most employees miss. OPM converts your unused sick leave balance into additional service credit at a rate of 2,087 hours per year.

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A full year of banked sick leave adds a full year of service credit to your annuity. Annual leave pays out as a one-time lump sum, but unused sick leave directly raises your pension for life.

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At roughly 1,000 unused hours, you gain about five months and 22 days of credit. One limit applies: according to OPM, unused sick leave can increase the annuity calculation, but you can't use it to meet retirement eligibility rules.

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Part-time service can be creditable, though OPM may prorate the annuity based on your work schedule. Periods of leave without pay that exceed six months in a calendar year are generally excluded.

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Your Service Computation Date can differ from your hire date because of breaks in service or military time. Verify it against your official personnel record before you estimate anything.

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Variable Three: The Multiplier and Why Age 62 Matters

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The multiplier is 1% per year of service for most retirees. It climbs to 1.1% only when you retire at age 62 or later with at least 20 years of creditable service. According to OPM, that 0.1 percentage-point difference raises your basic annuity calculation by 10% before reductions, permanently.

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This is one of the most consequential timing decisions in federal retirement. Take an employee with a $100,000 High-3 and 25 years of service.

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At the 1% rate, the annual pension is $25,000. At 1.1%, it's $27,500, a $2,500 yearly difference for the rest of retirement.

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The enhanced multiplier doesn't apply to disability retirements or MRA+10 retirements, so employees in those categories should confirm their specific multiplier with OPM. Certain special-category employees, including law enforcement officers, firefighters, and air traffic controllers, use a higher 1.7% multiplier for their first 20 years of service.

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FERS vs. CSRS: How the Two Systems Compare

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FERS replaced CSRS, the Civil Service Retirement System, for most federal employees who first entered covered service on or after January 1, 1987. CSRS pays a larger standalone pension because most CSRS employees receive neither Social Security nor a government match in the TSP (Thrift Savings Plan), the federal government's tax-advantaged retirement savings program.

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FERS pensions are smaller by design because they form one leg of a three-part structure. The table below compares the two systems on the points that affect your calculation.

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According to OPM, FERS is built so the pension, Social Security, and the TSP work together. These income streams are generally calculated separately, though your total income can affect taxes and Medicare premiums.

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The FERS Supplement: Bridging the Gap Before 62

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The FERS Supplement, also called the Special Retirement Supplement (SRS), generally goes to eligible employees who retire before age 62 with an immediate, unreduced annuity, including certain special-provision retirees. It isn't available in all retirement categories.

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According to OPM, the supplement approximates the Social Security benefit you earned during federal service, and it's paid until you reach age 62.

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OPM estimates the supplement by taking your projected Social Security benefit at 62 and multiplying it by a fraction: your years of FERS service divided by 40. An employee with an estimated $2,000 monthly Social Security benefit and 25 years of FERS service would receive roughly $1,250 per month ($2,000 × 25/40).

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The supplement carries an earnings test similar to Social Security's. According to the FERS supplement rules for 2026, the benefit drops by $1 for every $2 you earn above the annual exempt amount of $24,480, and it ends entirely at age 62 regardless of when you claim Social Security.

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Employees who retire under the MRA+10 provision don't receive the supplement at all.

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Reductions That Lower Your Final Pension

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Your calculated annuity is rarely your final check. Several reductions apply before the money reaches you, and planning for them prevents budget surprises.

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The most common is the survivor benefit election. According to OPM, electing a full 50% survivor annuity for your spouse reduces your pension by 10% for life. A 25% survivor benefit reduces it by 5%.

A $50,000 annuity with the full survivor election nets $45,000.

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The second is the early-retirement age reduction. Under MRA+10, retiring at your MRA, or Minimum Retirement Age, the earliest age a FERS employee can retire with an immediate annuity (currently 57 for those born in 1970 or later), with 10 to 29 years of service, OPM reduces your benefit by 5% for each year you are under age 62.

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Retiring at 57 instead of 62 is a 25% permanent cut, not a temporary one. OPM notes you can lessen or eliminate this reduction by postponing your annuity start date.

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Putting It Together: A Full Calculation Example

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Here is how the variables combine for a representative retiree, using the formula OPM publishes.

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A federal employee retires at age 62 with a $95,000 High-3 average salary and 28 years of creditable service, including a converted year of unused sick leave. She meets the age-62-plus-20-years threshold, so her multiplier is 1.1%.

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Her basic annuity is $95,000 × 28 × 1.1% = $29,260 per year, or about $2,438 per month before reductions. If she elects a full survivor benefit, the 10% reduction brings her to $26,334 per year.

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Her TSP withdrawals and Social Security then stack on top as independent income streams.

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Run the same employee at age 61, and the multiplier drops to 1%. That produces $26,600, a difference of $2,660 every year for life.

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The math is why timing your retirement date is one of the highest-value decisions you'll make as a federal employee. Federal Pension Advisors models these scenarios side by side so you can see the trade-offs before the paperwork is filed.

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Frequently Asked Questions

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1. How is the FERS pension calculated?

Your FERS pension equals your High-3 average salary multiplied by your years of creditable service multiplied by a 1% multiplier. According to OPM, the multiplier rises to 1.1% if you retire at age 62 or later with at least 20 years of service, raising your basic annuity calculation before reductions by 10% permanently.

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2. What is the High-3 in a FERS pension?

The High-3 is the average of your highest 36 consecutive months of basic pay. According to OPM, it includes base salary and locality pay but excludes overtime, bonuses, and awards. It's usually your final three years, but OPM always uses your highest-earning consecutive three-year period.

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3. Can I collect FERS and Social Security at the same time?

Yes. According to OPM, FERS is designed to be paid alongside Social Security. Many FERS retirees receive three income streams: the FERS basic annuity from OPM, Social Security benefits, and withdrawals from the Thrift Savings Plan. These are calculated separately, though total income can affect taxes and Medicare premiums.

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4. When can I retire with full benefits under FERS?

You can retire with an immediate, unreduced FERS annuity at your Minimum Retirement Age with 30 years of service, at age 60 with 20 years, or at age 62 with 5 years. According to OPM, retiring under MRA+10 triggers a permanent 5% reduction for each year you are under 62.

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5. How much should I contribute to my TSP?

Contribute at least 5% of your basic pay to capture the full government match, according to the Federal Retirement Thrift Investment Board. For 2026 the IRS-set elective deferral limit is $24,500, with an additional $8,000 catch-up for those 50 and older. Employees ages 60 to 63 may qualify for a higher 2026 catch-up limit of $11,250.

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6. Does unused sick leave count toward my FERS pension?

Yes. According to OPM, unused sick leave converts to creditable service at retirement at a rate of 2,087 hours per year. Annual leave pays out as a lump sum, but sick leave can increase your creditable service for annuity computation. You can't use it to meet retirement eligibility rules.

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Conclusion

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Your FERS pension comes down to three numbers: your High-3 average salary, your years of creditable service, and whether you qualify for the 1% or 1.1% multiplier. Each one responds to decisions you can still make, including when you retire, whether you buy back military time, how you bank sick leave, and which survivor election you choose.

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Federal pension content carries lifelong financial consequences, so confirm every figure here against your official OPM records and the current plan year's published limits before you file.

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Federal Pension Advisors builds retirement income models that combine your pension, TSP, Social Security, and FEHB into a single plan. To run your own numbers with a credentialed federal benefits specialist, schedule a federal retirement analysis with Federal Pension Advisors.

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Disclaimer

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This article is for educational purposes only and does not constitute financial, legal, tax, or retirement advice. Federal retirement benefits vary by employee record, service history, retirement category, and current OPM rules. Verify all figures with OPM.gov, TSP.gov, your agency HR office, and a qualified federal benefits professional before making retirement decisions. 

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