How It Works

Our iBond calculator uses official Treasury data to provide accurate, real-time valuations of your Series I Savings Bonds.

Key Features

Official Treasury Data

Our calculator pulls real-time interest rates directly from the U.S. Treasury's official data sources. All calculations are based on the same rates used by TreasuryDirect.gov.

Accurate Calculations

We use the official Treasury formula to calculate compound interest, including the complex interaction between fixed and variable rates that determines your bond's value.

Instant Results

Get your iBond value calculated instantly without visiting multiple government websites or doing complex math. Simply enter your purchase details and get results immediately.

Privacy Protected

Your personal financial information never leaves your device. All calculations are performed locally, ensuring your privacy and security.

How to Use the Calculator

1

Enter Purchase Amount

Input the dollar amount you invested in your iBond (minimum $25, maximum $10,000 per year).

2

Select Purchase Date

Choose the month and year when you purchased your iBond. The calculator supports bonds purchased from 1998 to present.

3

Get Your Results

Click "Calculate iBond Value" to see your current bond value, interest earned, and any applicable penalties.

Understanding Your Results

Current Value

The total value of your iBond today, including your original investment plus all accrued interest.

Interest Earned

The total amount of interest your iBond has earned since purchase, compounded semi-annually.

Current Rates

The current fixed rate, variable inflation rate, and composite rate affecting your bond's growth.

Early Redemption Penalty

If your bond is less than 5 years old, we show the penalty (3 months of interest) and your value after penalty.

Data Sources & Accuracy

Our calculator uses the following official data sources to ensure accuracy:

  • Historical Interest Rates: Official Treasury data from 1998 to present
  • Current Rates: Updated with each Treasury announcement (May and November)
  • Calculation Methods: Official Treasury formulas for compound interest and penalties

Important: While our calculator strives for accuracy, always verify important financial decisions with official Treasury sources or a financial advisor.