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I-Bond Calculator

Calculate returns on Series I Savings Bonds with current and projected inflation rates. See growth over time with the combined fixed + inflation rate.

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Understanding I-Bonds

Series I Savings Bonds are issued by the US Treasury and designed to protect purchasing power against inflation. The interest rate has two components: a fixed rate (set at purchase, lasts the life of the bond) and an inflation rate (adjusted every 6 months based on CPI-U). The composite rate formula: Fixed Rate + (2 × Inflation Rate) + (Fixed Rate × Inflation Rate). With a 1.3% fixed rate and 2.5% inflation: composite = 6.37%.

I-Bonds have unique advantages: state and local tax exempt, federal tax deferred until redemption, and inflation-protected. The maximum purchase is $10,000/year per person electronically (plus $5,000 via tax refund). They cannot be redeemed for 12 months, and redemption before 5 years forfeits the last 3 months of interest. After 5 years, no penalty. Compare with CDs using our CD Calculator and CD Ladder Calculator.

People Also Ask

What is the current I-Bond rate?
I-Bond rates change every May and November. Check TreasuryDirect.gov for the current composite rate. The fixed rate is set at purchase and never changes; the inflation component adjusts semiannually.
Are I-Bonds better than TIPS?
I-Bonds: better for small investors ($10K limit), state tax exempt, no market risk. TIPS: no purchase limit, tradeable, can lose value if sold before maturity. For most individuals, I-Bonds are simpler.
Can I buy I-Bonds for my children?
Yes — each person (including minors) can buy $10,000/year. A family of 4 can purchase $40,000/year in I-Bonds, plus $20,000 via tax refunds.
When should I redeem I-Bonds?
Hold at least 5 years to avoid the 3-month interest penalty. Ideal: hold 20-30 years for maximum compounding. Redeem when you need the money or when other investments offer better real returns.