How the I Bond Rate is Calculated The I Bond composite rate is a combination of a fixed rate and a variable rate that changes with inflation. The formula accounts for both components, creating a secure but inflation-responsive investment. For May 2025, the ibond rate prediction places the inflation-adjusted component at 2.86%, with a fixed rate of 1.1%, totaling an estimated 3.98%. ... https://www.federalpensionadvisors.com/post/i-bond-rates-prediction-2025