I Bond Calculator (Value & Interest)
Project the value of Series I savings bonds — composite rate from the fixed rate and inflation, semiannual compounding, and the 3-month interest penalty if you cash out before 5 years. Defaults to the May–October 2026 rates.
For information and education only — not financial advice. Results are estimates based on the numbers you enter; check important decisions with a qualified professional.
How to use
- 1Enter the amount and your bond's fixed rate (0.90% for bonds bought May–October 2026).
- 2Enter the inflation rate you expect.
- 3See the value by year and the effect of cashing out early.
How it's calculated
Composite rate = fixed + 2 × semiannual inflation + fixed × semiannual inflation. Interest compounds every 6 months. Redeeming before 5 years forfeits the last 3 months of interest; bonds can't be cashed in the first 12 months.
Frequently asked questions
What's the current I bond rate?
4.26% for bonds issued May 1 – October 31, 2026: a 0.90% fixed rate plus 3.34% annualized inflation. New rates are announced May 1 and November 1.
How much can I buy?
$10,000 per person per calendar year in electronic bonds through TreasuryDirect.
Are I bonds taxed?
Interest is exempt from state and local income tax. Federal tax is due when you cash them (or at 30 years), and may be excluded if used for qualified education expenses.