FERS vs TSP: How Federal Retirement Benefits Fit Together [2026]
FERS vs TSP explained: compare the FERS annuity, Social Security and TSP savings plan using current OPM and IRS rules.
FERS and TSP are not competing versions of one account: FERS is a federal retirement system that includes a basic annuity and Social Security coverage, while TSP is the defined-contribution savings plan. Compare the OPM annuity formula, agency matching rules, contribution limits, tax treatment, investment choices and eligibility using current plan documents.
Model TSP contribution and match assumptions separately from the FERS annuity and Social Security estimates; plan rules and limits must be verified first.
The federal retirement system that combines a basic annuity, Social Security coverage and the Thrift Savings Plan (TSP). The basic annuity uses a high-3 average salary and creditable service under OPM rules.
A defined-contribution retirement savings plan for federal employees and service members. Your balance depends on contributions, any agency or service contribution, investment performance, fees and withdrawals.
The highest average basic pay earned during any three consecutive years of creditable federal service, as defined by OPM; overtime and bonuses are generally excluded from basic pay.
FERS vs TSP is a comparison between a retirement system and one of its savings components. FERS combines a basic annuity, Social Security and TSP; TSP is the account where contributions are invested. A federal employee may use all three pieces, subject to eligibility and plan rules.
How the FERS annuity is calculated
OPM calculates the basic FERS annuity from your high-3 average salary and creditable service. The general formula is 1% of high-3 multiplied by years of service, or 1.1% when you separate at age 62 or older with at least 20 years of service. Special categories and transferred service can use different rules, so verify the OPM formula that applies to you.
What the TSP adds
TSP is the defined-contribution part of the federal retirement picture. Your outcome depends on employee contributions, any agency or service contribution available under your plan, investment selection, fees, withdrawals and tax treatment. Check the current TSP and agency notices rather than assuming a fixed match or rate.
A practical FERS vs TSP checklist
- Confirm your FERS coverage, service history and high-3 estimate with your agency or OPM.
- Read the current TSP and agency matching rules and contribute only an amount your budget can sustain.
- Check the current IRS elective-deferral limit and catch-up rules for the tax year; limits can change.
- Compare traditional and Roth tax treatment, fund choices, fees, liquidity and withdrawal rules in the plan documents.
- Model the TSP balance separately from the FERS annuity and Social Security; a calculator is a scenario tool, not an eligibility determination.
CSRS and transferred service
CSRS, CSRS Offset and transferred-service cases have different eligibility, formula and Social Security interactions. Do not apply a FERS shortcut to a CSRS or mixed record; use the OPM handbook and your retirement specialist for the applicable calculation.
The FERS annuity supplement
Some employees who retire before age 62 may qualify for a FERS annuity supplement, and an earnings test can reduce it. Eligibility and the calculation depend on the retirement path and service record; review the current OPM rules before including it in a plan.
Use the 401(k) calculator for a contribution and match scenario, then keep the FERS annuity and Social Security estimates separate. The arithmetic cannot determine federal eligibility, a benefit award or the tax result of a withdrawal.
Frequently asked questions
What is the difference between FERS and TSP?
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Is FERS better than TSP?
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How is the FERS pension calculated?
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What is the 2026 TSP contribution limit?
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Sources & further reading
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