TSP Calculator

The Thrift Savings Plan is the federal defined-contribution retirement plan authorized for service members under 5 U.S.C. § 8440e. The plan is administered by the Federal Retirement Thrift Investment Board (FRTIB), not by DFAS or the service branches. Service members participate in the same TSP vehicle as civilian federal employees, but the matching rules differ depending on retirement system eligibility — Blended Retirement System (BRS) members receive employer matching; pre-2018 High-3 members do not.

The BRS 5% match — automatic 1% plus dollar-for-dollar through 4%. Under the BRS matching rules (5 U.S.C. § 8432(c), as applied to members via § 8440e; Public Law 114-92), the Department of Defense contributes 1% of basic pay to the member's TSP regardless of whether the member contributes, beginning after 60 days of service. The member who contributes 5% or more of basic pay receives a 4% matching contribution from the government, structured as a dollar-for-dollar match on the first 3% and 50 cents on the dollar on the next 2% (DoD FMR Vol. 7A, Ch. 51, Table 51-4). The combined employer contribution at the 5% member contribution level is 5% — the "free 5%" worth capturing before prioritizing most other savings vehicles. Contributing less than 5% leaves matching dollars on the table; a service member at 5% under BRS who reduces to 3% gives back the 0.5% match × 2% = 1% of basic pay per year. Timing matters: for auto-enrolled BRS members the automatic 1% starts with the pay period on or after the 60th day of service, but the matching portion does not start until the pay period after 24 months of service, and both the automatic 1% and the match stop at the end of the pay period in which the member reaches 26 years of service (DoD FMR Vol. 7A, Ch. 51, paras. 4.5.1 and 4.5.2).

2026 contribution limits. The IRS-set annual elective deferral limit for 2026 is $24,500 for participants under age 50, with an additional $8,000 catch-up contribution available for participants age 50 and over (and an $11,250 super catch-up for ages 60–63 under SECURE 2.0). These limits are published annually by the IRS (Notice 2025-67 for the 2026 retirement plan limitations) and apply uniformly to TSP and to private-sector 401(k) plans. Members who max the $24,500 limit before December 31 stop receiving the employer match for the remainder of the year because matching is calculated per pay period — front-loading contributions to hit the cap in June or July creates a back-half match gap. For participants age 50+, the spillover method (effective January 1, 2021; TSP Bulletin 19-5) automatically applies contributions beyond the elective-deferral limit toward the catch-up limit, and those spillover contributions remain eligible for agency matching — but only up to the 5% of pay already matched (DoD FMR Vol. 7A, Ch. 51, para. 3.7.1).

Combat Zone Tax Exclusion contributions. Service members in a designated combat zone under 26 U.S.C. § 112 can keep contributing past the $24,500 elective deferral cap — but only in the Traditional bucket. A member who reaches the elective deferral limit while serving in a CZTE area may continue making Traditional contributions from tax-exempt pay, which count against the annual additions limit instead (DoD FMR Vol. 7A, Ch. 51, para. 3.2.2.2). Roth contributions stay capped at the $24,500 elective deferral limit even when funded from combat-zone pay (para. 3.2.2.1). The $72,000 (2026) annual additions limit under 26 U.S.C. § 415(c) is a ceiling on totalcontributions — your own contributions plus the agency automatic 1% and agency matching — not $72,000 of member money on top of the match, and for a member serving in a combat zone all contributions must stop once that combined ceiling is reached (paras. 3.2.2.3 and 3.2.2.4). Note also that the TSP cannot accept traditional tax-exempt contributions toward the catch-up limit (para. 3.7.2), so a member age 50+ cannot fund the $8,000 catch-up with CZTE pay in the Traditional bucket. On the way out, tax-exempt Traditional contributions are returned tax-free but the earnings on them are taxable; only qualified Roth distributions are tax-free on both contributions and earnings.

Roth vs Traditional under BRS. Both Roth and Traditional contributions count toward the 5% match threshold; the match itself goes to a Traditional (pre-tax) bucket regardless of the member's election. Junior enlisted members typically come out ahead with Roth because their marginal tax rate in service is often lower than their projected retirement rate. Senior officers approaching O-5 to O-6 with high taxable base pay are often better served by Traditional contributions because their marginal rate in service is already elevated. The TSP recordkeeper allocates each contribution to the correct sub-account; the calculator above models both elections.

Authorities: 5 U.S.C. §§ 8432(c), 8440e (uniformed-services TSP participation and agency automatic/matching contributions); Public Law 114-92 (BRS); 26 U.S.C. §§ 112, 402(g), 415 (CZTE, elective deferral limit, annual additions limit); IRS Notice 2025-67 (2026 retirement plan limitations); DoD FMR Vol. 7A, Chapter 51, paras. 3.2.2.1-3.2.2.4 (TSP contributions in a CZTE area) and paras. 4.5-4.8 (BRS agency contributions and vesting); FRTIB regulations (5 CFR Parts 1600-1690); Deputy Secretary of Defense Memorandum, "Implementation of the Blended Retirement System" (January 27, 2017). The FRTIB tsp.gov member portal is the authoritative source for contribution status, allocation percentages, and historical fund performance.