I-Bond Calculator (Series I Savings Bonds)
Calculate Series I Savings Bond value with current composite rate. See early redemption penalty and year-by-year growth.
Value at Maturity
$11,668.45
Total Interest
$1,668.45
Effective Annual Return
3.13%
I Bond Summary
| Purchase Amount | $10,000.00 |
| Value Before Penalty | $11,668.45 |
| Final Value | $11,668.45 |
| Total Interest Earned | $1,668.45 |
| Effective Annual Return | 3.13% |
Use the I-Bond Calculator (Series I Savings Bonds) above to calculate your results. Enter your values and see instant results — all calculations run in your browser.
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How It Works
Our I-Bond Calculator precisely determines the future value of your Series I Savings Bonds, incorporating the current composite rate and illustrating year-over-year growth. This tool is crucial for financial planning, allowing you to project your bond's worth and understand potential early redemption penalties. For example, if you purchase an I-Bond in early 2026, its initial composite rate will reflect the prevailing inflation and fixed rates for that period.
The calculator compounds the bond's value semi-annually based on its issue date, applying the composite rate, which is a combination of the fixed rate (set at purchase) and the semiannual inflation rate (adjusted every six months). It then deducts three months of interest if redeemed within the first five years, accurately reflecting the early redemption penalty. The calculation accounts for interest accrual up to 30 years or until redemption.
Always remember that I-Bond interest is tax-deferred until redemption or maturity. A common mistake is forgetting the three-month interest penalty for redemptions within five years; this calculator explicitly factors that in. The fixed rate component of your I-Bond never changes, but the inflation component adjusts, impacting your bond's overall growth.
Example: $10,000 I-Bond Purchased in January 2026
- 1 Input: Purchase Amount = $10,000; Purchase Date = January 2026; Holding Period = 3 years; Assumed Fixed Rate (for 2026) = 1.30%; Assumed Annual Inflation Rate (for 2026-2029) = 3.20%
- 2 Calculation: The calculator first determines the initial composite rate (Fixed Rate + 2 * Semiannual Inflation Rate). For a 1.30% fixed rate and 3.20% annual inflation, the initial composite rate would be 1.30% + (2 * (3.20% / 2)) = 4.50%. This rate is applied semi-annually. After 3 years, the accrued interest is calculated, and then three months of interest are subtracted for the early redemption penalty.
- 3 Intermediate Result: After 3 years, the bond's value before penalty is approximately $11,424. The interest accrued in the final three months of the holding period is roughly $120.
- 4 Final Result: After applying the early redemption penalty, the estimated redemption value of your $10,000 I-Bond purchased in January 2026 after 3 years would be approximately $11,304.
Source: SEC · Last updated: April 2026
Frequently Asked Questions
What is the current I-Bond rate for 2026?
How much can I buy in I-Bonds per year?
When can I cash in my I-Bonds without penalty?
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