Treasury Securities ("T-Secs", also known as TCM, or CMT, or T-Sec) values are calculated by the Treasury Department and reported by the Federal Reserve in Publication H.15. Below, you will find current and historical weekly yields for 3 month, 6 month Treasuries, as well as values for 1-, 2-, 3-, 5-, 7-, 10-, 20-, and 30 year treasuries.
The official name of this index is "Yield on U.S. Treasury Security Adjusted to a Constant Maturity of One Year" (or 6 months, or 2 years, etc.). Confusion can arise when lenders use the term "One Year Treasury Bill"; the 52-week bill is a completely different index, and rarely used on ARMs. To be certain, check your mortgage contract for the specific language.
Treasuries have both monthly and weekly values; for ARMs, the weekly value is most often used. Since it's often paired with ARMs that have annual rate adjustments, the most common version used is the One Year Treasury Security. Most frequently, your new interest rate will be determined by the index value 30 to 45 days before your next scheduled rate change; check your mortgage Note or Adjustable Rate Rider for details. A margin is added to this index by the lender when your ARM's rate is adjusted.
You can compute your new mortgage rate as soon as the relevant index value is released; see our ARM Check Kit for complete instructions and worksheets. Need monthly treasury index values instead?