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TSP Funds Explained: G, F, C, S, and I

Q: Should I use a Lifecycle fund instead of picking my own?

If you'd rather not build and rebalance your own mix, an L Fund diversifies and de-risks automatically by target date. Building your own mix gives more control if you'll actually maintain it.

Updated June 2026 · ~6 min read

The Thrift Savings Plan keeps things refreshingly simple: instead of hundreds of confusing options, you get five core index funds, each a single letter. Here's what G, F, C, S, and I actually hold, how risky each is, and how to think about combining them.

The five core funds at a glance

Fund	What it holds	Risk
G	Special U.S. Treasury securities issued just for the TSP	Lowest — can't lose value
F	U.S. investment-grade bonds (a broad bond index)	Low to moderate
C	Large U.S. company stocks (S&P 500)	Higher
S	Small and mid-size U.S. company stocks	Highest of the U.S. stock funds
I	International stocks (developed and emerging markets outside the U.S.)	Higher, plus currency swings

The G Fund — the safe harbor

The G Fund invests in government securities issued specially for the TSP. Its key feature: the share price never goes down. You won't get rich on it — returns are modest — but you also can't lose your principal. It's where many people park money they can't afford to risk, or shift toward as they near retirement.

The F Fund — bonds

The F Fund tracks a broad U.S. investment-grade bond index. It usually earns a bit more than the G Fund over time, but unlike the G Fund its price can fall — especially when interest rates rise. It adds diversification because bonds often (though not always) behave differently from stocks.

The C, S, and I Funds — the growth engines

These are the stock funds, where most long-term growth comes from — along with most of the short-term ups and downs.

C Fund: the 500 largest U.S. companies (the S&P 500). The classic "U.S. stock market" exposure.
S Fund: the rest of the U.S. market — small and mid-cap companies not in the S&P 500. Historically a bit more volatile than the C Fund, with strong long-run growth.
I Fund: stocks of companies outside the United States, across developed and emerging markets. Adds global diversification, but also exposes you to currency movements.

How to think about mixing them

There's no single "right" allocation, but a few principles hold for most people:

Time horizon drives risk. The further you are from needing the money, the more you can lean toward stock funds (C/S/I), which have historically out-earned G and F over long periods.
Closer to retirement, more stability. As your timeline shortens, shifting some money toward G and F reduces the chance a downturn hits right when you need to withdraw.
Diversify rather than chase. Picking last year's best fund rarely works. Spreading across funds smooths the ride.
Don't forget inflation. Playing it too safe for decades can mean your money doesn't grow enough to keep up with rising costs.

If choosing and rebalancing a mix sounds like work, the TSP's Lifecycle (L) Funds do it for you automatically.

Sample allocations by time horizon

These are illustrative starting points, not advice — your own risk tolerance and other income (like a pension) should shape the final mix:

Stage	Example mix	Idea
Early career (20s–30s)	~80–100% C/S/I	Long horizon; maximize growth and ride out volatility
Mid career (40s)	~60–80% C/S/I, rest G/F	Still growth-tilted, begin adding ballast
Near retirement (~5–10 yrs out)	~40–60% C/S/I, rest G/F	Protect gains against a badly timed downturn
In retirement	Heavier G/F, some stocks	Stability with enough growth to outpace inflation

Common fund mistakes

Parking everything in the G Fund for decades. It can't lose value, but it also may not outpace inflation over a long career.
Chasing last year's winner. The best-performing fund rotates; diversification beats prediction.
Holding an L Fund plus individual funds without realizing it skews your overall allocation.
Reacting to headlines. Selling stock funds during a dip locks in losses; a steady plan usually wins.

Model different return assumptions in the calculator →

Frequently asked questions

Which TSP fund is best?

There's no single best fund — it depends on your time horizon and risk tolerance. Younger investors often lean on the stock funds (C/S/I) for growth, while those near retirement add G and F for stability. Diversifying across funds usually beats betting on one.

What's the difference between the C, S, and I funds?

The C Fund holds large U.S. companies (S&P 500), the S Fund holds small and mid-size U.S. companies, and the I Fund holds international stocks. Together they cover the U.S. and global stock markets.

Is the G Fund safe?

Yes — its share price never falls and principal is guaranteed. The trade-off is the lowest long-run growth, so relying on it exclusively for decades risks not keeping up with inflation.

Should I just use a Lifecycle fund instead?

If you'd rather not build and rebalance your own mix, yes — an L Fund diversifies and de-risks automatically by target date. Building your own mix gives more control if you'll actually maintain it.

This article is for general education only and is not financial advice. CalculateTSP is independent and not affiliated with, endorsed by, or sponsored by the U.S. Department of Defense, DFAS, or the Federal Retirement Thrift Investment Board. Fund details can change; confirm current information at tsp.gov.