Last Updated: October 14, 2026 Reading Time: 9 min

A TSP growth calculator answers one question: if I keep putting this much in and the market returns that much, what will the balance be in 10, 20 or 30 years? The answer depends on four inputs you control or assume, and the honest version of the tool shows you how much each one moves the result. This guide gives you the formula, a grid you can read your own number off, the FERS match rules that quietly add 5% of salary to your inflow, and the cost of being one percentage point wrong about returns. Then it points you at our calculator, with a plain statement of what it does and does not model.

The Formula Behind Every TSP Projection

Every growth calculator, including ours, is doing some version of this:

Future value = PMT × [((1 + r/12)^(12n) − 1) ÷ (r/12)]

PMT is your total monthly inflow, employee contribution plus agency contribution. r is the nominal annual return. n is the number of years. The tables below use monthly compounding, contributions credited at the end of each month, a $0 starting balance, a flat salary for the whole period, and a nominal return before inflation and before expenses. For 2025, TSP.gov shows total core-fund expense ratios ranging from 0.034% to 0.051%, or 34 to 51 cents per $1,000.

Four things move the number: how much goes in each month, the return you assume, how long it compounds, and whether you capture the full agency share.

What the Agency Adds, and When It Does Not

If you are FERS, your employing agency contributes an automatic 1% of basic pay every pay period under 5 U.S.C. § 8432(c)(1), whether or not you contribute anything. If you do contribute, 5 U.S.C. § 8432(c)(2) adds a match: 100% of the first 3% of basic pay you put in and 50% of the next 2%. Contribute 5% and the agency contributes 5%, so 10% of basic pay goes in. Dollars above 5% earn no match.

"Basic pay" for this purpose is the rate used for your retirement deductions under 5 C.F.R. § 1690.1, and under 5 U.S.C. § 5304(c)(2)(A) locality pay is basic pay for FERS retirement. So the salary you enter in a projection is base plus locality. Our GS Pay Calculator gives you that figure for your grade, step and locality.

Three limits on the match matter for a projection:

  • It is paid per pay period, only when you contribute. Under 5 U.S.C. § 8432(c)(2)(A) the match attaches to a pay period in which the employee contributes. If you reach the annual limit in pay period 20, the match stops for the last six periods and only the 1% automatic continues. Spreading $24,500 across 26 pay periods is $942.31 per period. The front-loading match loss post walks through the cost.
  • The automatic 1% can be forfeited. Under 5 U.S.C. § 8432(g)(2) and 5 C.F.R. § 1603.3, the automatic 1% and its earnings are forfeited if you separate before completing 3 years of civilian service, or 2 years for certain SES, Executive Schedule and policy positions, and Members and congressional employees. Uniformed service members under the Blended Retirement System have a separate two-year vesting rule under the uniformed services' TSP provisions. Your own contributions and the match are "fully nonforfeitable when made," and nothing is forfeited if you die while still employed.
  • CSRS employees get none of it. Under 5 U.S.C. § 8351(b)(3) no agency contributions are made for CSRS participants. The linked growth mode assumes FERS agency contributions and cannot directly model CSRS, so treat its agency-match line as not applying to you.

Uniformed service members under the Blended Retirement System have their own contribution provisions under the uniformed services' TSP provisions, separate from the civilian rules above. The BRS match post covers that side.

The Grid: Projected Balance by Salary, Contribution Rate and Return

Assumptions, which apply to every cell: monthly compounding; contributions credited at the end of each month; $0 starting balance; flat salary for the whole period with no step increases or COLAs; nominal return before inflation and before expenses; employee contribution of 5%, 10% or 15% of basic pay plus the full 5% agency share, which requires contributing at least 5%. Cells are rounded to the nearest $100 from unrounded computation.

Salary You contribute Total inflow Monthly inflow 5% return: 10 / 20 / 30 yrs 7% return: 10 / 20 / 30 yrs 9% return: 10 / 20 / 30 yrs
$60,000 5% 10% $500 $77,600 / $205,500 / $416,100 $86,500 / $260,500 / $610,000 $96,800 / $333,900 / $915,400
$60,000 10% 15% $750 $116,500 / $308,300 / $624,200 $129,800 / $390,700 / $915,000 $145,100 / $500,900 / $1,373,100
$60,000 15% 20% $1,000 $155,300 / $411,000 / $832,300 $173,100 / $520,900 / $1,220,000 $193,500 / $667,900 / $1,830,700
$90,000 5% 10% $750 $116,500 / $308,300 / $624,200 $129,800 / $390,700 / $915,000 $145,100 / $500,900 / $1,373,100
$90,000 10% 15% $1,125 $174,700 / $462,400 / $936,300 $194,700 / $586,000 / $1,372,500 $217,700 / $751,400 / $2,059,600
$90,000 15% 20% $1,500 $232,900 / $616,600 / $1,248,400 $259,600 / $781,400 / $1,830,000 $290,300 / $1,001,800 / $2,746,100
$120,000 5% 10% $1,000 $155,300 / $411,000 / $832,300 $173,100 / $520,900 / $1,220,000 $193,500 / $667,900 / $1,830,700
$120,000 10% 15% $1,500 $232,900 / $616,600 / $1,248,400 $259,600 / $781,400 / $1,830,000 $290,300 / $1,001,800 / $2,746,100
$120,000 15% 20% $2,000 $310,600 / $822,100 / $1,664,500 $346,200 / $1,041,900 / $2,439,900 $387,000 / $1,335,800 / $3,661,500

Computed by FedTools with the formula above. Annuity factors per $1 a month: 5% → 155.28 / 411.03 / 832.26; 7% → 173.08 / 520.93 / 1,219.97; 9% → 193.51 / 667.89 / 1,830.74 for 10 / 20 / 30 years. No cell exceeds the 2026 deferral limit; the largest employee contribution is 15% of $120,000, or $18,000.

Read across any row and the lesson is the horizon: at 7%, the $90,000 earner contributing 10% has $194,700 after 10 years and $1,372,500 after 30. Read down and the lesson is the rate of contribution, not the salary: $60,000 at 15% and $120,000 at 5% are the same $1,000 a month and land on the same balance.

Spot-check: the smallest cell is $500 a month at 5% for 10 years: 500 × 155.28 ≈ $77,641 using the unrounded factor, rounded to $77,600. The largest is $2,000 × 1,830.74 ≈ $3,661,487 using the unrounded factor, rounded to $3,661,500.

What One Point of Return Costs

The return assumption is the input people argue about, so here is its price. At $1,000 a month for 30 years:

Assumed return Balance after 30 years Total contributed Growth
6% $1,004,500 $360,000 $644,500
7% $1,220,000 $360,000 $860,000
8% $1,490,400 $360,000 $1,130,400

Same assumptions as the grid. Annuity factors for 30 years: 1,004.52 / 1,219.97 / 1,490.36.

One point is worth about $215,500 between 6% and 7% and about $270,400 between 7% and 8%. That is why a projection should be read as a range. Our calculator's presets are 5%, 7% and 9%, with a custom field for any rate. TSP.gov's own illustration uses a 6.8% average annual return, under which every $1 invested grows to $10 in 35 years. For context, the C Fund's 10-year annualized return through December 2025 was 14.79% and the G Fund's was 2.76%, per TSP.gov data as reported in our G Fund analysis; a blended lifecycle-style mix lands between them.

The 2026 Limits and the Per-Paycheck Math

The IRS published the 2026 limits on November 13, 2025 in Notice 2025-67. The elective deferral limit is $24,500. Participants age 50 and older can add an $8,000 catch-up, for $32,500. Participants age 60 through 63 get an $11,250 catch-up instead of the $8,000, for $35,750, not $43,750. The 2027 limits had not been announced when this was written; expect them in November.

Age band 2026 annual limit Per pay period over 26
Under 50 $24,500 $942.31
50 to 59, and 64 and over $32,500 $1,250.00
60 to 63 $35,750 $1,375.00

Years with 27 pay periods change the per-period figure; see the 27-pay-period election change post. The full 2026 limit detail is in TSP limits 2026.

Roth, Traditional and Where the Match Goes

The TSP's Roth option is a qualified Roth contribution program under 5 U.S.C. § 8432d and Internal Revenue Code § 402A. Your own contributions can be traditional, Roth or a mix. The agency's money cannot. Agency automatic and matching contributions are deposited to the traditional balance (5 C.F.R. § 1690.1). Eligible traditional amounts can later be converted to Roth under the in-plan conversion rules. A 100% Roth saver still retires with a taxable traditional balance unless eligible amounts are converted. That is TSP regulation; the tax code itself would allow Roth matching, but the TSP does not do it. The trade-offs are in Roth vs traditional for federal employees, and moving existing traditional money to Roth inside the plan is covered in the in-plan Roth conversion guide.

Run Your Own Projection

Use our free TSP Calculator in growth mode: enter your current balance, current age, retirement age, annual salary, your contribution as a percentage of salary or an annual dollar amount, your traditional-versus-Roth split, and a return scenario of 5%, 7%, 9% or a custom rate. It returns your balance at retirement, your own contributions, the agency match, investment growth, years to retirement, a year-by-year table and the traditional-versus-Roth split. Project your TSP balance

Two things to know about how it computes. For FERS employees contributing at least 1% of salary, it figures the 1% and the match for you from your salary and contribution percentage, so do not add them yourself. It accepts contributions below 1% of salary but does not compute the matching for them, so its match is incorrect in that range, and it does not model a CSRS zero-agency selection. And it compounds once a year with the year's contributions credited at the start of the year, so for the same monthly inflow its results can differ from the monthly-compounding tables in this guide by up to about 3% in either direction. It does not model salary growth, inflation, fees or fund-level returns; use the custom rate field to stress-test a point either side of your assumption.

Frequently Asked Questions

How much will my TSP grow in 10, 20 or 30 years?

It depends on your monthly inflow and the return you assume. At $1,000 a month, which is a $120,000 salary at 5% plus the 5% agency share, and a 7% return, the grid gives $173,100, $520,900 and $1,220,000, with monthly compounding, a flat salary and a nominal return.

What return rate should I use to project my TSP?

Our calculator's presets are 5%, 7% and 9%, and TSP.gov's own illustration uses 6.8%. Per TSP.gov data as reported in our G Fund analysis, the C Fund's 10-year annualized return through December 2025 was 14.79% and the G Fund's 2.76%, so a blended mix lands between them. Run two rates and read the result as a range.

Does the agency match count in the projection?

Yes for FERS: 1% automatic plus 100% of your first 3% and 50% of the next 2%, computed on basic pay including locality. Contribute 5% and 10% of salary goes in. CSRS participants get no agency contributions.

What does a 1% difference in return cost over 30 years?

On $1,000 a month, about $215,000 between 6% and 7%, or about $270,000 between 7% and 8%.

Does the FedTools TSP calculator include the match automatically?

Yes, for FERS employees contributing at least 1% of salary. Enter your salary and contribution percentage and it computes the 1% and the match and reports it separately as agency match; it does not model the match for contributions below 1% or a CSRS zero-agency selection. It compounds annually with contributions credited at the start of the year, so its results can differ from the monthly-compounding tables here by up to about 3% in either direction.

Is the 2026 super catch-up added on top of the regular catch-up?

No. Ages 60 to 63 get $11,250 instead of $8,000, for $35,750 in total, not $43,750.

What happens to the agency 1% if I leave before 3 years?

The automatic 1% and its earnings are forfeited if you separate before 3 years of civilian service, or 2 years for certain SES, Executive Schedule and policy positions, and Members and congressional employees. Uniformed service members under the Blended Retirement System have a separate two-year vesting rule. Your own contributions and the match are fully nonforfeitable when made, and nothing is forfeited if you die in service.

If I max out early, do I lose the match?

The match is paid only for pay periods in which you contribute. Hitting $24,500 in pay period 20 means six periods with no match; only the 1% automatic continues. Spreading the limit evenly over 26 pay periods, $942.31 each, avoids it; check your agency's 2026 pay-period count.

If I contribute 100% Roth, is the agency match Roth too?

No. By TSP regulation the automatic 1% and the match are deposited to your traditional balance; eligible traditional amounts can later be converted to Roth under the in-plan conversion rules.

Sources: IRS IR-2025-111 / Notice 2025-67, 2026 limits; 5 U.S.C. § 8432; 5 U.S.C. § 8351; 5 U.S.C. § 8432d; 5 U.S.C. § 5304; 26 U.S.C. § 402A; 5 C.F.R. § 1690.1; 5 C.F.R. § 1603.3; TSP.gov fund performance; TSP.gov expenses and fees; TSP.gov, Grow with the TSP.