How to Find the Interest Accrued on an I-Series Bond

Series I savings bonds allow you to save money in a tax-advantaged investment with minimal risk: You'll get your money back unless the U.S. government defaults on its debts. Series I bonds earn interest for up to 30 years and you don't have to pay federal taxes on the interest until you cash out. Plus, you never pay state or local income taxes. I bonds earn interest monthly and the interest compounds every six months. The interest rate is a combination of a fixed rate that remains the same over the life of the I bond and a variable rate that adjusts for inflation twice a year.

Go to the U.S. Department of the Treasury's website and click on "Tools," "Savings Bond Calculator" and "Get Started."

Select "I Bonds" from the dropdown menu below "Series."

Select the face value of the bond from the dropdown menu below "Denomination." For example, if your I bond is a $100 bond, select "100."

Enter the "Value as of" date in the first window in the calculator. Enter the month and year of the bond's issue date below "Issue Date," then click "Calculate." For example, if the bond was issued in October 2011, enter "10/11." The website will show the amount of interest your bond has accrued up to the "Value as of" date.


  • You don't need to enter the serial number of the bond to check its value. But, you can save your bond inventory on the TreasuryDirect website so you can check the updated values faster in the future.


  • You can cash in your I savings bonds as soon as 12 months after you purchase them. However, if you cash them before five years pass, you lose the last three months of interest as an early withdrawal penalty.
  • If your I bond is less than 5 years old, when you use the TreasuryDirect calculator, it will not include the last three months of interest because of the penalty.

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About the Author

Mark Kennan is a writer based in the Kansas City area, specializing in personal finance and business topics. He has been writing since 2009 and has been published by "Quicken," "TurboTax," and "The Motley Fool."