Thrift Savings PlanThe F Fund is the Thrift Savings Plan’s bond fund. It tracks a broad index of investment-grade U.S. bonds — Treasuries, agency and mortgage-backed securities, and corporate debt — and it is the fund most federal employees misunderstand, because bonds can and do lose money.
The F Fund is not a safer version of the G Fund. It is a market-priced fund with real downside, as 2022 demonstrated.
The F Fund returned 3.41% a year over 2006–2025. It did its job in 2008 (+5.45%) and failed it in 2022 (−12.83%, its worst year of the period) because rising interest rates push bond prices down — the same force that was hitting stocks. Diversification by bond fund is real, but it is not a guarantee.
What the F Fund actually holds
The F Fund is an index fund tracking the Bloomberg U.S. Aggregate Bond Index — a basket covering the investment-grade U.S. bond market: U.S. Treasury and government agency issues, mortgage-backed securities, and corporate bonds. You own thousands of individual bonds through one fund, all of them investment-grade, none of them junk.
Because those bonds trade on the open market, the F Fund’s value moves with interest rates. When rates rise, existing bonds paying lower coupons are worth less, and the fund’s share price falls. That is the mechanism behind every negative year in the table below.
What the F Fund costs
TSP administrative expenses are among the lowest of any retirement plan in the country, and the TSP publishes a net expense ratio for every fund each year. We do not print a figure here, because our data source covers returns rather than the fee schedule and we only publish numbers we can point to — check the current published net expense ratio for the F Fund on tsp.gov. What matters for a decision is the ranking: TSP costs are low enough that they are almost never the reason to choose one of these funds over another. Choose on risk and role instead.
Risk profile: modest returns, real losses
The F Fund is much steadier than the three stock funds — its worst year, −12.83%, is a third of the C Fund’s worst — but it is a market fund, not a guarantee. It had three negative years in twenty (2013, 2021 and 2022); 2018 was barely positive at +0.15%. Over the full period, $10,000 became $19,571.
The comparison that matters for a TSP investor is not F Fund versus stocks, it is F Fund versus G Fund. The F Fund earned about half a percent more a year over these twenty years — and to get it, you accepted a 12.83% loss in the single year you most wanted a cushion.
F Fund annual returns, 2006–2025
| Year | F Fund return |
|---|---|
| 2006 | 4.40% |
| 2007 | 7.09% |
| 2008 | 5.45% |
| 2009 | 5.99% |
| 2010 | 6.71% |
| 2011 | 7.89% |
| 2012 | 4.29% |
| 2013 | -1.68% |
| 2014 | 6.73% |
| 2015 | 0.91% |
| 2016 | 2.91% |
| 2017 | 3.82% |
| 2018 | 0.15% |
| 2019 | 8.68% |
| 2020 | 7.50% |
| 2021 | -1.46% |
| 2022 | -12.83% |
| 2023 | 5.58% |
| 2024 | 1.33% |
| 2025 | 7.21% |
Calendar-year returns for the F Fund, January 2006 through December 2025. Click a column heading to sort — sorting by return is the fastest way to see the best and worst years. Source: Portfolio Visualizer export used for the Retirement Edge TSP backtest.
2008, 2020 and 2022 — the F Fund in the three stress tests
2008: +5.45%. Textbook behaviour. Stocks collapsed, high-quality bonds rose, and a stock-and-bond mix lost less than stocks alone.
2020: +7.50%. Its second-best year of the period. Falling rates lifted bond prices while the stock funds whipsawed.
2022: −12.83%. The year the hedge broke. The C Fund fell 18.13%, the S Fund 26.26% — and the F Fund fell with them, because the cause was rising rates rather than a growth scare. The G Fund returned +2.98% in the same year. If you hold the F Fund as your protection, 2022 is the year to study before the next one.
Who the F Fund suits — and who it does not
It suits you if you want a bond sleeve that can appreciate when rates fall and pays more than the G Fund over long stretches, and you understand it can have a losing year.
It does not suit you if you are treating it as guaranteed money, or if you would sell it after a year like 2022. In the TSP, the fund that behaves like cash is the G Fund — not this one.
The other TSP funds
- C FundLarge-cap U.S. stocks · 11.01%
- S FundSmall and mid-cap U.S. stocks · 9.53%
- I FundInternational stocks · 5.91%
- G FundGovernment securities · 2.85%
- All five, side by sideThe TSP funds hub
The part a table cannot tell you
How much of the F Fund to hold, and when that should change, is the actual question. Our TSP allocation by age guide gives a decade-by-decade framework, you can pressure-test any mix in the TSP Calculator, and the TSP Edge model portfolio is a rules-based monthly update built from these same five funds — research you choose to act on, with most months saying nothing needs to change.