Wealthy PotTSP Funds Explained: G, F, C, S, I and the L Funds, With Returns and Costs
The Thrift Savings Plan offers 16 funds: five individual index funds (G, F, C, S and I) and eleven Lifecycle (L) Funds that mix those five for you. Over the 10 years to September 30, 2026, the C Fund returned 15.30% a year and the G Fund 2.97% a year, and every fund costs between 0.034% and 0.051% a year. This guide covers what each fund holds, how risky it is, its returns and costs, and the rules for moving money between them.
Table of Contents
The Short Answer
- G Fund: special Treasury securities that cannot lose principal. Lowest risk, lowest long-run return.
- F Fund: investment-grade US bonds tracking the Bloomberg U.S. Aggregate Bond Index.
- C Fund: the S&P 500, the 500 large US companies that make up about 88% of the US stock market's value.
- S Fund: the rest of the US market, 3,375 small and mid-sized companies at the end of 2025.
- I Fund: over 5,100 companies in 44 countries outside the US, excluding China and Hong Kong.
- L Funds: eleven ready-made mixes of the five, from L Income to L 2075, that get more conservative as their target date approaches.
New civilian employees enrolled on or after September 5, 2015, and members of the Blended Retirement System, are invested by default in the L Fund for their age. Everyone else defaults to the G Fund until they choose.
The Five Individual Funds
| Fund | Tracks | What it holds | TSP risk rating |
|---|---|---|---|
| G Fund | No index; earns a statutory interest rate | Treasury securities issued only to the TSP | Low |
| F Fund | Bloomberg U.S. Aggregate Bond Index | Investment-grade US bonds: 46.9% government, 26.1% securitized, 27.1% corporate and other credit; 13,940 issues at end-2025 | Low-medium |
| C Fund | S&P 500 Index | 500 large US companies | Medium |
| S Fund | Dow Jones U.S. Completion Total Stock Market Index | US stocks not in the S&P 500 (3,375 at end-2025) | Medium-high |
| I Fund | MSCI ACWI IMI ex USA ex China ex Hong Kong Index | Large, mid and small companies in developed and emerging markets | High |
Source: tsp.gov fund pages and TSP Fund Information sheets (data as of December 31, 2025).
The G Fund is unique to the TSP. Its interest rate resets monthly and, by law, equals the average market yield on Treasury notes and bonds with 4 or more years to maturity. So you get a long-term bond yield with no chance of losing principal: the TSP says "the value of G Fund securities does not fluctuate; only the interest rate changes." The risk is inflation. Over long stretches it has trailed stocks by a wide margin. Its rate also sets the interest on TSP loans.
The F Fund is a broad investment-grade bond fund. Unlike the G Fund it can lose value when interest rates rise, as it did in 2022 (down 12.83%). The index's average duration was 5.8 years at the end of 2025, which the TSP translates as a 5.8% price drop for a 1-point rise in rates. Our bonds primer explains why bond prices move against rates.
The C and S Funds together cover essentially the whole US stock market. The S&P 500 is about 88% of US market value and the Completion index the other 12%, so a C-and-S mix in roughly an 88/12 ratio comes close to the total market. The C Fund is concentrated at the top: the largest 100 companies were about 75% of the index at the end of 2025.
The I Fund changed benchmarks in 2024. It tracked the MSCI EAFE Index, which covered developed markets only, through July 31, 2024. It then moved to the MSCI ACWI IMI ex USA ex China ex Hong Kong Index, and the TSP announced the switch complete on October 30, 2024. The new index adds emerging markets such as Taiwan and small companies, and leaves out China and Hong Kong. Japan was the largest country weight at 16.1% at the end of 2025, followed by the United Kingdom (9.8%) and Canada (9.2%). The I Fund also carries currency risk: a stronger dollar lowers its return in dollars.
TSP Fund Returns
Annualized returns after expenses, as of September 30, 2026, from tsp.gov's rates-of-return data:
| Fund | 1 year | 3 years | 5 years | 10 years | Since inception |
|---|---|---|---|---|---|
| G Fund | 4.51% | 4.50% | 3.97% | 2.97% | 4.64% (1987) |
| F Fund | -1.77% | 4.07% | -0.57% | 1.23% | 5.12% (1988) |
| C Fund | 15.72% | 22.85% | 13.76% | 15.30% | 11.45% (1988) |
| S Fund | 11.82% | 18.73% | 6.23% | 11.19% | 9.60% (2001) |
| I Fund | 23.06% | 21.20% | 10.96% | 10.06% | 6.46% (2001) |
Source: TSP rates of return data file, trailing periods ending September 30, 2026. Past performance does not predict future returns.
Three things stand out. The F Fund has lost money over five years, because the period includes the 2022 bond decline. The G Fund beat the F Fund over 10 years (2.97% vs 1.23%) with no price risk at all. And single years swing hard: the I Fund returned 32.45% in calendar 2025 but lost 13.94% in 2022, when the S Fund lost 26.26%.
The L Funds
Each L Fund holds all five individual funds in a target mix. Every quarter the TSP shifts the mix toward the G and F Funds as the target date nears, and it rebalances every trading day. When an L Fund reaches its year it is folded into L Income, which is what happened to L 2025 on June 30, 2025, the same day L 2075 opened. The TSP's suggested fund by birth year:
| Fund | Suggested for birth years | 1 year | 3 years | 5 years | 10 years | Since inception |
|---|---|---|---|---|---|---|
| L Income | Before 1965, or already withdrawing | 7.88% | 9.05% | 6.10% | 5.43% | 4.75% |
| L 2030 | 1965-1969 | 11.61% | 14.70% | 8.62% | 9.15% | 7.52% |
| L 2035 | 1970-1974 | 12.92% | 15.92% | 9.14% | n/a | 11.24% |
| L 2040 | 1975-1979 | 13.65% | 16.93% | 9.55% | 10.31% | 8.24% |
| L 2045 | 1980-1984 | 14.29% | 17.80% | 9.87% | n/a | 12.47% |
| L 2050 | 1985-1989 | 14.96% | 18.67% | 10.23% | 11.26% | 10.29% |
| L 2055 | 1990-1994 | 17.70% | 21.72% | 11.78% | n/a | 15.35% |
| L 2060 | 1995-1999 | 17.70% | 21.72% | 11.78% | n/a | 15.34% |
| L 2065 | 2000-2004 | 17.70% | 21.72% | 11.77% | n/a | 15.34% |
| L 2070 | 2005-2009 | 17.69% | n/a | n/a | n/a | 18.42% |
| L 2075 | After 2009 | 17.69% | n/a | n/a | n/a | 20.50% |
Source: tsp.gov Lifecycle fund pages and rates-of-return data, periods ending September 30, 2026. n/a = fund not old enough. L 2035, 2045, 2055, 2060 and 2065 opened July 1, 2020; L 2070 on July 26, 2024; L 2075 on June 30, 2025, so their since-inception figures cover short, strong stretches.
The birth-year bands are a suggestion only. If you plan to work past your mid-60s, or have a pension and Social Security covering most of your spending, a later-dated fund may fit better. The reverse holds if you will need the money sooner. Do not hold an L Fund alongside individual funds without checking the overlap: the L Fund already owns all five, so adding more C Fund on top quietly makes you more aggressive than the L Fund you picked.
What the TSP Costs
The TSP publishes one total expense ratio per fund. For 2025:
| Fund | Total expense ratio (2025) | Cost per $10,000 a year |
|---|---|---|
| G Fund | 0.034% | $3.40 |
| F Fund | 0.035% | $3.50 |
| C Fund | 0.035% | $3.50 |
| S Fund | 0.051% | $5.10 |
| I Fund | 0.048% | $4.80 |
| L Funds | 0.035% (L Income) to 0.041% | $3.50 to $4.10 |
Source: tsp.gov Expenses and fees. The L Funds have no separate fee; their ratio is the blend of the funds they hold.
The TSP's own example: $100,000 in the C Fund paid $35 in 2025. Part of the plan's administrative cost is covered by forfeited 1% automatic contributions from employees who leave before they are vested, which is one reason the net figure is so low. For comparison with retail funds, see our guide to index funds and ETFs.
Changing Your Investments
The TSP has three kinds of investment transaction:
- Investment election: where new money goes, including contributions, the agency match, rollovers in and loan repayments. It does not move money already in your account.
- Reallocation (formerly called an interfund transfer): redistributes your whole existing balance into new percentages.
- Fund transfer: moves money from specific funds to other specific funds and leaves the rest alone.
The two-per-month rule: in each calendar month, your first two reallocations or fund transfers, in any combination, can go into any fund. After that, for the rest of the month, you can only move money into the G Fund. Investment elections are not limited. Transactions made before noon Eastern time are generally processed that business day.
A common mistake is to change the investment election and assume the existing balance moved too. It did not. To change both, make an investment election and a reallocation.
The Mutual Fund Window
The mutual fund window lets you put part of your account into outside mutual funds. The rules:
- The first transfer must be at least $10,000 and no more than 25% of your balance, so you need at least $40,000 in the TSP.
- No more than 25% of your account can be in the window at any time.
- Fees: a $37 annual administrative fee plus a $95 annual maintenance fee ($132 a year in total), plus $28.75 per trade, plus each fund's own expenses.
- Contributions cannot go straight into the window, and loans and withdrawals cannot come straight out of it.
Hypothetical example: on a $40,000 window balance, the $132 in annual fees alone is 0.33% a year before any trade fee or fund expense. That is roughly ten times the C Fund's total cost. For most people the window only makes sense for a specific fund the TSP lacks, held for a long time with little trading.
Choosing a Mix
If you do not want to manage it, the L Fund for your expected withdrawal date is a reasonable default and costs the same as the funds inside it. If you prefer to build your own, the usual starting point is stocks (C, S and I) for money you will not touch for many years and G for money you will need soon, with the balance shifting toward G as retirement approaches. Some retirees keep a few years of planned withdrawals in the G Fund so they never have to sell stocks after a crash. Our guide to a sustainable withdrawal strategy covers that approach.
Whatever you pick, run it through the TSP calculator to see what it means in dollars, and compare it with your other accounts using our TSP vs 401(k) vs IRA comparison. For the plan's other rules, including the 5% match and contribution limits, see the Thrift Savings Plan guide.
Sources & Methodology
- TSP, Rates of return, and its underlying data file, for all returns (trailing periods ending September 30, 2026; calendar years 2022 and 2025).
- TSP, What is an individual fund? and What is a Lifecycle Fund?, for objectives, risk ratings, inception dates and birth-year bands.
- TSP Fund Information sheets (TSPLF14), for holdings, index details and the I Fund benchmark dates.
- TSP, I Fund benchmark index change complete (October 30, 2024) and Changes to two lifecycle funds (June 30, 2025).
- TSP, Expenses and fees, for 2025 expense ratios.
- Summary of the TSP (TSPBK08, January 2026), for default investments and transaction rules.
- TSP, Mutual fund window, for eligibility and fees.
Method notes. Returns are TSP's published annualized figures after expenses. "Cost per $10,000" and the mutual fund window percentage are our own arithmetic on TSP's published rates. Since-inception figures for funds less than a few years old cover a short period and are not comparable with the older funds.
This article is for general information and is not financial advice. Figures are from tsp.gov and TSP publications, checked against the primary sources on 2026-10-04. Returns change monthly, past performance does not guarantee future results, and the right mix depends on your own timeline and other income.
FAQ
What are the 5 TSP funds?
The G Fund (government securities), F Fund (bonds, Bloomberg U.S. Aggregate), C Fund (S&P 500), S Fund (US stocks outside the S&P 500) and I Fund (international stocks, excluding the US, China and Hong Kong). The L Funds are mixes of these five.
Which TSP fund has the best return?
Over 10 years to September 30, 2026, the C Fund, at 15.30% a year. Over one year the I Fund led at 23.06%. Higher returns came with bigger drops: the C Fund lost 18.13% in 2022 while the G Fund gained 2.98%.
Can the G Fund lose money?
Not in principal. Its securities are guaranteed by the US government and their value does not fluctuate; only the monthly interest rate changes. It can lose ground to inflation.
What does the I Fund invest in now?
Since 2024 it tracks the MSCI ACWI IMI ex USA ex China ex Hong Kong Index: over 5,100 large, mid and small companies in 44 countries, including emerging markets, but not China or Hong Kong. Before August 2024 it tracked the developed-market MSCI EAFE Index.
What is the default TSP fund?
For civilians enrolled on or after September 5, 2015, and BRS members, the L Fund for your age. For anyone else, the G Fund until you make an investment election.
How many times can I move money between TSP funds?
Two reallocations or fund transfers per calendar month into any fund. After that, only into the G Fund for the rest of the month. Changing where future contributions go is not limited.
Which L Funds are available in 2026?
Eleven: L Income, L 2030, L 2035, L 2040, L 2045, L 2050, L 2055, L 2060, L 2065, L 2070 and L 2075. L 2025 closed into L Income on June 30, 2025.
What are TSP expense ratios?
For 2025, 0.034% for the G Fund up to 0.051% for the S Fund. That is 34 to 51 cents a year per $1,000 invested.
Cite This Page
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"TSP Funds Explained: G, F, C, S, I and the L Funds, With Returns and Costs." Wealthy Pot, 2026. https://wealthypot.com/tsp-funds/
