I Bond Calculator
Calculate the current value, interest earned, and future value of Series I Savings Bonds issued by the US Treasury. Enter your bond details to get an estimate.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator estimates the current and future value of a U.S. Series I Savings Bond based on its denomination, issue date, fixed rate, and the latest semi-annual inflation rate.
- Select Denomination: Choose the bond’s face value ($50 to $1,000) from the dropdown.
- Enter Issue Date: Pick the month and year the bond was purchased using the date picker.
- Input Fixed Rate (%): Enter the bond’s fixed annual rate at issue (e.g., 0.10 for 0.10%).
- Input Current Semi-Annual Inflation Rate (%): Enter the latest semi-annual inflation rate (e.g., 1.69 for 1.69%).
- Enter Months Held: Specify how many months you’ve held the bond (1 to 360).
- Click “Calculate”: The results will show:
- Current Value: Estimated value after the months held.
- Interest Earned: Total interest accrued so far.
- Future Value (30 years): Projected value if held to full maturity.
The composite rate is calculated as: fixed rate + (2 × semi-annual inflation rate) + (fixed rate × semi-annual inflation rate). All rates must be entered as percentages (e.g., 0.10 for 0.10%).
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Frequently Asked Questions
An I Bond (Series I Savings Bond) is a US Treasury savings bond that earns interest based on a fixed rate and a semi-annual inflation rate, protecting against inflation.
Composite rate = fixed rate + (2 × semi-annual inflation rate) + (fixed rate × semi-annual inflation rate). The fixed rate is set at purchase and the inflation rate is updated every six months.
Yes, but there is a penalty of the last 3 months of interest if redeemed within the first 5 years. After 5 years, no penalty.
