TSP Calculator
A TSP calculator shows how a Thrift Savings Plan (TSP) balance can grow over time. It uses the same compound-growth math as a 401(k) or IRA projection, with the government's automatic and matching contributions added on top.
The TSP is the federal government's retirement savings plan for federal employees and uniformed service members, and it is built similarly to a private-sector 401(k). In the calculator above, enter your starting balance, your own monthly contribution, your expected annual return, and your time horizon.
Then check the match formula below to see how much extra your agency or service adds to what you contribute.
How it's calculated
The calculator above applies the standard future-value formula to your own contributions: FV = PV×(1+r)^n + PMT×((1+r)^n − 1)/r, where PV is your starting balance, PMT is your monthly contribution, r is your monthly return, and n is your number of months. That's the identical engine behind every projection on this site, whether the account is a TSP, a 401(k), or a taxable brokerage account. What makes the TSP different isn't the math. It's the government contribution layered on top of whatever you enter, which this section explains in prose since the exact match depends on rules the calculator's formula doesn't model.
According to the Thrift Savings Plan's own published contribution rules, most FERS (Federal Employees Retirement System) employees and eligible uniformed service members under the Blended Retirement System (BRS) receive two kinds of government money on top of their own contributions. First, an Agency/Service Automatic Contribution equal to 1% of basic pay, deposited every pay period whether or not the employee contributes anything. Second, an Agency/Service Matching Contribution on the first 5% of pay contributed: the first 3% is matched dollar-for-dollar, and the next 2% is matched at 50 cents on the dollar. Contribute the full 5% of pay, and the agency or service adds a total of 5% on top, the 1% automatic contribution plus 4% in matching. Contribute less than 5% of pay, and part of that match goes uncollected. Contribute more than 5%, and the extra beyond 5% receives no additional match, though it still grows in the account.
This calculator does not compute the match automatically, since eligibility, vesting, and the exact percentage contributed all affect the number. To model a TSP with the government match included, add the expected match to the monthly contribution field by hand. For example, contributing 5% of a $6,000 monthly salary is $300, and qualifying for the full 5% total match adds $300 in agency money, $60 automatic plus $240 matching, so enter $600 as the monthly contribution to reflect the combined total that lands in the account each month.
Vesting works differently for the two types of agency money under FERS. Contributions from the employee, and the Agency/Service Matching Contribution, are vested immediately, so that money belongs to the employee from day one. The Agency/Service Automatic (1%) Contribution is different: most FERS employees vest in it only after 3 years of federal service, or 2 years for certain positions, per TSP's own published vesting rules. Leaving federal service before hitting that requirement forfeits the unvested automatic contributions and their earnings back to the TSP. Uniformed service members under the BRS follow a simpler rule, vesting in both the automatic 1% and the matching contributions after 2 years of service.
A worked example
Say you earn $75,000 a year, or $6,250 a month, and contribute 5% of your pay, $312.50 a month, the amount needed to capture the full match. The agency adds another $312.50 a month, the 1% automatic contribution plus the 4% match combined, so $625 a month lands in the TSP account total.
Starting with $10,000 already saved and assuming a 7% annual return over 25 years, the calculator above projects a balance of about $563,500 when entering the combined $625 monthly contribution. Enter only the employee's own $312.50, leaving the match out entirely, and the same calculator projects about $310,400 instead.
The agency match alone accounts for roughly $253,100 of that gap, more than 80% of what the employee's own contribution built by itself.
Common mistakes to avoid
- Contributing less than 5% of pay and leaving free money on the table. Every percent below 5% is a percent of guaranteed matching the agency doesn't send, money no market return can make up for.
- Assuming this calculator automatically adds the match. It doesn't model matching or vesting rules on its own, so add the expected agency contribution to the monthly contribution field by hand.
- Forgetting the vesting clock on the automatic 1% contribution. Separating from federal service before 3 years (2 for certain positions, or 2 for BRS service members) forfeits any unvested automatic contributions.
- Treating TSP fund returns like a single guaranteed rate. The TSP's own C, S, I, F, and G funds each carry very different long-run returns and risk levels, so the return entered should match the specific fund mix actually held.
- Ignoring the annual contribution limit. TSP contributions share the same Internal Revenue Service (IRS) elective-deferral limit as a private 401(k), so check the current-year limit on tsp.gov before assuming an unlimited amount can be contributed.
Frequently asked questions
What is the TSP?
The Thrift Savings Plan (TSP) is the federal government's retirement savings and investment plan for federal employees and uniformed service members, run by the Federal Retirement Thrift Investment Board. It works much like a private-sector 401(k): contribute a portion of pay, choose from a set menu of funds, and the balance grows tax-deferred, or tax-free in the Roth TSP, until retirement.
How much does the government match in the TSP?
For most FERS employees and BRS-covered service members, the government adds a 1% automatic contribution to pay whether or not the employee contributes anything, then matches contributions dollar-for-dollar on the first 3% of pay and 50 cents on the dollar on the next 2%. Contribute 5% of pay, and the government adds a total of 5%, per TSP's own published contribution rules.
Do I need to contribute the full 5% to get any match?
No, the match scales with what you contribute, up to the 5% cap. Contributing 3% gets the 1% automatic contribution plus a dollar-for-dollar match on that 3%, for 4% total agency money. Contributing 5% gets the full 5% agency total. Contributing above 5% adds nothing further from the government, though the extra employee contributions still grow.
How does TSP vesting work?
Employee contributions and the Agency/Service Matching Contribution are vested immediately. The separate 1% Agency Automatic Contribution has its own vesting period: most FERS employees vest after 3 years of federal service, or 2 years for certain positions, and BRS service members vest in both the automatic and matching contributions after 2 years of service. Leaving before the vesting date forfeits the unvested automatic contributions.
What return rate should I use for the TSP calculator?
Match the rate to the specific TSP fund or fund mix held, since the TSP's C (common stock), S (small-cap), I (international), F (fixed income), and G (government securities) funds carry very different long-run returns and risk levels. A conservative, G Fund-heavy allocation should use a lower rate than a C Fund-heavy, large-cap stock allocation. Check the specific fund's published performance data on tsp.gov rather than assuming one number fits every TSP account.
Is a Roth TSP different from a traditional TSP in this calculator?
The growth math is identical either way, since compounding doesn't know or care about tax treatment. What differs is what happens at withdrawal: a traditional TSP is taxed as ordinary income when withdrawn, while a Roth TSP's qualified withdrawals are tax-free, similar to the difference between a traditional and Roth IRA. The government match itself always goes into the traditional side of the account, even when the employee's own contributions are Roth.
Does this calculator account for TSP contribution limits?
No, it has no field enforcing the annual limit, so the entered monthly contribution needs to stay realistic on its own. TSP contributions share the same IRS elective-deferral limit as a private 401(k), and that limit changes most years, so check the current figure on tsp.gov before planning a monthly contribution around it.
Sources
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