I Bond Rate Calculator
Combine the fixed rate and semiannual inflation rate to estimate the current U.S. Series I Bond composite yield.
Informational calculation only; not investment advice.
Examples
- Fixed 0.90%, inflation 1.97% ⇒ 4.86% annual, 2.43% per 6 months
- Fixed 0.40%, inflation 3.56% ⇒ 7.53% annual, 3.76% per 6 months
FAQ
Where do I find the semiannual inflation rate?
Use the latest CPI-U announcement from the U.S. Treasury, expressed as a percentage change over six months.
Does the calculator account for the 3-month interest penalty?
No, it reports the official composite rate before any redemption penalties.
Can the composite rate be negative?
No, Treasury floors the combined rate at 0%, even if inflation is negative.
Additional Information
- TreasuryDirect publishes new fixed and inflation components each May and November.
- The composite rate never falls below zero; negative inflation can offset but not exceed the fixed rate.