Federal Retirement Income Calculator: FERS Pension + TSP + Social Security

Federal retirement has three income streams — FERS pension, Social Security, and TSP withdrawals. Most employees know roughly what each piece is worth in isolation. What they actually need to know is: how much will I get each month, phase by phase? This calculator computes your FERS pension directly from your High-3 salary and years of service, adds your FERS supplement (the automatic bridge payment before age 62), adds Social Security, and shows how much TSP you need to fill the gap — all in monthly dollars, with a 2026 federal tax estimate.

How the three-legged stool works in federal retirement

Most retirement planning tools are built for the private sector — one income stream (portfolio withdrawals) sized to replace a salary. Federal employees under FERS have a fundamentally different structure: a defined-benefit pension that covers a guaranteed floor of expenses, an automatic supplement that bridges the gap from early retirement to age 62, full Social Security benefits (FERS employees pay FICA taxes and earn full SS credits), and a TSP balance that serves as a flexible layer above the pension floor.

The practical result: a federal employee with a $60,000/year FERS pension, a $28,000 Social Security benefit, and a $700,000 TSP balance may only need their TSP to cover a small fraction of spending — or nothing at all in Phase 2. That changes the retirement math entirely compared to a private-sector worker facing the same numbers.

FERS pension: the guaranteed floor

The FERS basic annuity formula: 1.0% × High-3 salary × years of service. If you retire at age 62 or older with at least 20 years of service, the multiplier rises to 1.1% — worth about $1,200/year more per $100,000 of High-3 salary for a 30-year employee. Special category employees (law enforcement, firefighters, air traffic controllers) use an enhanced formula: 1.7% for the first 20 years, then 1.0% for years beyond 20, with earlier eligibility (age 50 with 20+ years).⁵

The survivor benefit election reduces your monthly check by 5% (partial) or 10% (full) — a real cost, but it keeps your spouse in the FEHB system if you die first, and provides 25% or 50% of your basic annuity as lifetime income for them. Electing "none" requires your spouse's written consent and permanently removes their FEHB eligibility should you predecease them.

FERS supplement: the bridge to age 62

Federal employees who retire under an immediate, unreduced FERS annuity before age 62 receive the FERS Special Retirement Supplement automatically — no application required. The formula: (FERS years ÷ 40) × estimated SS benefit at 62. For 30 years of service and an estimated SS of $21,000 at 62, the supplement is $15,750/year ($1,312/month), paid from your retirement date until you turn 62, regardless of when you claim Social Security.³

Two traps: the supplement ends the month you turn 62 regardless of when you claim SS — so if you delay SS to 67 or 70, you have a gap. And a 2026 earnings test reduces the supplement dollar-for-dollar above $24,480 in earned income if you work part-time after retirement. TSP withdrawals, pension income, and investment returns do not count against the earnings test.²

TSP: the flexible income layer

In Phase 1 (before Social Security), TSP fills the gap between your pension + supplement and your spending goal. In Phase 2 (after SS), the pension + SS stack often covers most or all spending — at which point the TSP either isn't needed or generates small withdrawals. Because the pension reduces the baseline TSP withdrawal rate dramatically, most FERS retirees' portfolios are far more durable than a private-sector worker in the same position would experience under the standard 4% rule.

Key nuances: Traditional TSP withdrawals are fully taxable as ordinary income. Roth TSP withdrawals are tax-free. In-plan Roth conversions (launched January 28, 2026) let you convert Traditional TSP to Roth while still in the TSP — useful during the low-bracket window between retirement and RMD age. See our in-plan Roth conversion guide for mechanics.