On Wednesday, April 30, the U.S. Treasury Department announced that Series I savings bonds issued from May through October 2025 will earn an annualized composite rate of 3.98%, an increase from the prior 3.11%. The new rate includes a variable component of 2.88% and a fixed rate of 1.10%, compared to the previous combination of 1.90% variable and 1.20% fixed.
Series I bonds are government-backed savings bonds that offer a low-risk way to invest while guarding against inflation. Their interest rate is a combination of a fixed rate, which remains the same for the life of the bond, and a variable rate tied to inflation, which adjusts every six months based on changes in the Consumer Price Index for all Urban Consumers (CPI-U).
Latest Rate Breakdown
The Treasury updates I bond rates twice each year, on May 1 and November 1. For the current cycle, the Treasury set the fixed rate at 1.10%, alongside a semiannual inflation variable rate of 1.43%, based on the CPI-U increase from 315.301 in September 2024 to 319.799 in March 2025 – a six-month rise of 1.43%.
Using the Treasury’s official formula:
Composite rate = fixed rate + (2 × semiannual inflation rate) + (fixed rate × semiannual inflation rate)
Plugging in the current figures:
0.0110 + (2 × 0.0143) + (0.0110 × 0.0143) = 0.0398 → Composite rate: 3.98%
Buying I Bonds
Electronic I bonds can be purchased through TreasuryDirect.gov in any amount from $25 up to $10,000 per person each calendar year. As of 2025, the option to buy an additional $5,000 in paper I bonds through federal tax refunds has been discontinued.
I bonds must be held for at least 12 months. If redeemed within the first five years, investors lose the last three months of interest.
