G Fund Rate: TSP G Fund Interest Rate

The G Fund invests in special Treasury securities that pay a long-term interest rate but can be redeemed at face value on any business day. Your balance cannot fall in dollar terms; only the rate changes, once a month. It can still lose purchasing power: tsp.gov notes the G Fund may not grow enough to offset inflation. When the monthly rate goes up, your earnings accrue faster, and when it falls they accrue more slowly. TSP reports each month’s earnings as a monthly return.

The rate is an annual figure. TSP’s own monthly return usually matches the rate multiplied by the days in the month and divided by the days in the year; some months differ by about 0.01 percentage point. 4.875% over September 2026, for example, was a 0.40% monthly return.

Rate versus return. The G Fund rate is the interest rate for one month. A rate of return, such as the 1-year return of 4.51%, is what the fund actually earned over a longer period, so it blends many monthly rates. Use the rate when you want the current level (for example, to see what a TSP loan costs) and the return to see how the fund did.

Congress set the formula in 5 U.S.C. 8438(e). Each month the Treasury computes the average market yield, from market quotations as of the end of the previous month, of all outstanding marketable Treasury securities that are not due or callable for at least 4 years, and the result is rounded to the nearest one-eighth of 1 percent. TSP’s fund sheet describes about 202 securities weighted by amount outstanding, with a weighted average maturity of about 13 years.

Because the formula follows long-term Treasury yields, the rate moves when those yields move, and it cannot be predicted precisely. This page does not publish forecasts; a month appears in the table only after TSP has published it.

Monthly G Fund rates and returns from December 2022 through September 2026. TSP does not publish a month-by-month rate table, so each rate was read from TSP’s “current loan interest rate” data as shown the month after (the loan rate is the previous month’s G Fund rate); the monthly return is TSP’s own figure. 31 of 46 months have a rate on record. For the other 15, we could not read an official value, so the table says so rather than estimating one. December 2022 is left blank because TSP’s own return for that month (0.32%) does not fit the 3.875% in the archived file. Each rate links to the TSP file it was read from, so you can check it yourself.

TSP’s calendar-year G Fund returns since 1988. The latest year is year to date through September 2026, not a full year.