Which rate belongs to an existing holding?
This chart records rates announced for new issue windows. The fixed component stays with each issue, while the semiannual inflation component changes. An existing holding can have a different composite rate from the newest advertised one. Its earning periods begin in its issue month and repeat every six months.
Use the I Bond Calculator with your actual issue date. A January issue changes its inflation component in January and July; a May announcement does not reset it immediately. The composite column here describes new issues in that row’s window.
Composite rate formula
The annual composite equals fixed rate + twice the semiannual inflation rate + their product in decimal form. It is rounded to 0.01% with a minimum of zero. The inflation column is the six-month input, not an annualized return. A negative input can offset the fixed component without reducing previously accumulated principal.
How the next I bond rate is calculated
The inflation component uses the non-seasonally adjusted CPI-U for all items in the U.S. city average, published by the Bureau of Labor Statistics. The May announcement uses March’s index compared with the preceding September. The November announcement uses September’s index compared with March of the same year.
Semiannual inflation = (later CPI-U index − earlier CPI-U index) ÷ earlier CPI-U index. Express the change as a percentage and round it to 0.01%. Once both endpoint indexes have been published, this formula supplies the inflation component.
Treasury determines the new fixed rate separately; CPI-U alone does not determine it. Combine the applicable fixed rate with the inflation component using the composite formula above, including its rounding and zero floor. A future purchase rate remains unknown until Treasury announces the fixed component.
Sources checked October 3, 2026: 31 CFR 359.10–359.14 and Appendix C, and TreasuryDirect’s rate explanation.
Announcement dates and source updates
Rates are effective May 1 and November 1. Publication can move to the next business day when the date falls on a nonbusiness day, while the effective date remains unchanged. Future rates remain unknown until Treasury publishes them.
Historical records were checked against TreasuryDirect’s web history, spreadsheet and rate-chart PDF on October 3, 2026. The complete table and chart are static HTML and SVG, available without JavaScript. The methodology distinguishes rate verification from value-file comparisons.
Questions about your bond
Is the inflation column an annual interest rate?
The inflation column is a six-month input. Treasury doubles that component and combines it with the fixed component and their product to calculate the annual composite rate. The final result is rounded and has a zero floor. Read the labeled columns separately rather than treating the inflation figure as an annual return.
Will a November announcement change every I holding immediately?
The announcement provides the inflation component for upcoming six-month earning periods. A holding adopts it when its own next period begins, based on the issue month. A November issue can change in November, while a January issue changes in January. The original fixed component remains part of the resulting composite rate.
Content updated 2026-10-03. Information only; not financial or tax advice.