Support

Questions, problems, or suggestions? Email support@tspgfundforecast.com. We usually reply within a few business days.

How is the estimate calculated?

By law (5 U.S.C. §8438), the G Fund rate for a month is the average market yield, on the last business day of the prior month, of all marketable U.S. Treasury securities with more than four years left to maturity, rounded to the nearest 1/8 percent. Each business evening the app reads Treasury's published yield curve at each qualifying note's and bond's remaining maturity, weights each by the amount outstanding (from Treasury's Monthly Statement of the Public Debt), and rounds the result.

When does it update?

Business-day evenings, after Treasury publishes that day's yield curve. There is no update on weekends or on days the bond market is closed, such as Columbus Day, Veterans Day, and other federal holidays.

How accurate is it?

The estimate made on the last business day of each month is the app's prediction for the next month's rate. The Track Record tab compares each of those predictions with the rate TSP published. Earlier in the month the estimate moves with Treasury yields, so it can change from day to day.

Why can the estimate flip back and forth?

When the unrounded average sits close to the halfway point between two eighths (a "boundary"), a small move in yields can change which eighth it rounds to. The app shows how far the estimate is from the nearest boundary so you can tell a firm estimate from a coin flip.

Where does the official rate come from?

The Thrift Savings Plan publishes the official G Fund rate, usually within a day or two of the start of the month. This app is not affiliated with the TSP.

TSP G Fund Forecast is not affiliated with, endorsed by, or connected to the Federal Retirement Thrift Investment Board or the Thrift Savings Plan. Estimates only — not financial advice.