Banking & Savings
I-Bond Interest Calculator
Project Series I Savings Bond value from fixed and inflation rates, including the early-redemption penalty.
Enter your details
$
%
02
%
-15
months
1360
Your result
Redemption value
$10,764.64
Composite rate 4.26% → worth $10,764.64 after 24 months (after 3-month interest penalty). I-Bonds can't be cashed in the first 12 months.
Interest earned
$764.64
Composite rate
4.26%
Early-withdrawal penalty
$113.91
About this calculator
Series I Savings Bonds combine a fixed rate (set at purchase, for life) with an inflation rate that resets every May and November: composite = fixed + 2×inflation + fixed×inflation. Redeeming before 5 years forfeits the last 3 months of interest; the composite rate never goes below 0%.
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