vs. OPM Calculator
OPM's tool does one thing well: it estimates your basic annuity. But FERS retirement involves seven interconnected decisions — and six of them aren't in the calculator.
The core distinction
These are different tools solving different problems. The FERS Benefits Calculator does estimation well. It was not designed for the second question.
What each tool can answer — and what it can't.
Estimates your basic annuity for a single retirement date. Accurate, official, and useful as a starting point. It was designed to answer one question: "What will my pension be if I retire on this date?"
Comparing multiple retirement ages. Modeling the FERS Supplement cliff. Checking FEHB eligibility. Weighing the survivor election. Projecting TSP to retirement. Most employees don't have a tool that does all of this together — until now.
The gaps
The FERS Benefits Calculator gives you a pension estimate for a single retirement date you enter. To compare retiring at 57 vs. 62, you have to run it twice, write both numbers down, and do the math yourself.
FedHorizon runs all three ages simultaneously — pension, supplement, TSP balance, and cumulative lifetime income — and states the break-even age explicitly.
A GS-13 with 28 years of service retiring at 57 instead of 62 may receive $605 less per month in pension — a gap worth over $200,000 in cumulative lifetime income by age 85. Without side-by-side modeling, that number stays invisible.
Cumulative lifetime income
Retire at 57 vs. 62 — where the lines cross
Cumulative lifetime income · Example: High-3 $108k, 28 YOS · Your numbers will vary
The FERS Supplement is the pre-Social Security bridge payment — worth $800–$1,500/month for eligible retirees — that fills the income gap between MRA and age 62. The FERS Benefits Calculator does not include it in projections.
The supplement is modeled in every scenario. You see how much it adds at your MRA, the month it stops at 62, and what happens to your income then — whether Social Security replaces it or leaves a gap your TSP has to cover.
A retiree at MRA with 30 years of service may receive $1,350/month in supplement payments for five years — $81,000 that stops on a fixed, calculable date. Not knowing this number before you retire means not planning for it.
Interactive — adjust your numbers
Your income at every age from MRA to 70
The FERS Benefits Calculator estimates your basic annuity — it doesn't model the three survivor election options side-by-side, show the monthly cost of each, or show what each one protects if you die first.
All three elections (0%, 25%, 50%) are modeled side-by-side. You see the monthly cost and your spouse's monthly benefit if you die first. A 25% election costs 5% of your pension for life — that math deserves more than a footnote.
Electing full survivor benefits on a $3,500/month pension costs $350/month — over $4,000/year — for the rest of your life. Whether that pays off depends on how long you and your spouse each live. That trade-off is not in the official tool.
Side-by-side election comparison
What each survivor election costs — and protects
Example: Diane, $3,246/mo pension at 60 · costs are ~5% / ~10% of the pension; the spouse receives 25% / 50% of the unreduced pension
Losing federal health coverage at retirement is one of the most consequential and least reversible retirement mistakes. OPM's calculator doesn't ask about your enrollment history or flag the 5-year rule.
Every report checks continuous FEHB enrollment against the 5-year requirement. If you're at risk of losing coverage, it's flagged — not buried in a handbook you'd have to find yourself.
If you have prior military service, a FERS buyback deposit can add years to your pension calculation. OPM's basic calculator doesn't model this — the deposit amount, the annuity increase, or the payback period.
Military buyback is calculated in full: deposit amount (3% of military pay + interest), the pension increase it unlocks, and the break-even period. For many veterans the deposit pays back within a few years of retirement.
Your FERS pension is only one leg of the three-legged stool. OPM's retirement calculator doesn't factor in TSP balance projections, drawdown strategy, or how your TSP interacts with pension and Social Security timing.
TSP balance is projected to your retirement date using your allocation and contribution rate, then shown alongside pension and estimated Social Security as a combined monthly income picture.
OPM's calculator estimates a basic annuity but doesn't prompt for employee type or apply the Special Category rules automatically. LEO, firefighter, ATC, CBPO, and NMC employees have a 1.7% accrual rate for the first 20 covered years, different mandatory retirement ages, and earlier VERA eligibility — none of which are surfaced in a standard annuity estimate.
Standard LEO, firefighter, ATC, CBPO and nuclear materials courier retirements are supported. Select your employee type and the 1.7% accrual rate, immediate retirement at 50 with 20 years (or any age with 25), and your mandatory separation age are applied automatically. See the methodology page for known limitations.
The free instant estimate shows your pension and FERS Supplement in seconds. The full report adds what OPM's calculator skips — survivor election cost, FEHB eligibility, and side-by-side retirement ages.