Savings Bond Calculator
US savings bonds grow quietly for decades. This calculator projects a Series EE bond (fixed rate, with the Treasury’s 20-year doubling guarantee applied) or a Series I bond (composite rate, compounded semiannually) from the rate you enter.
Results
Formula
How to use this calculator
- Choose the series of your bond.
- Enter the purchase amount and the bond’s current stated rate.
- Enter how long you plan to hold it, then Calculate.
Worked example
A $100 Series EE bond at a 3% fixed rate held 10 years.
- Value: 100 × 1.03¹⁰ ≈ $134.39.
- Interest earned: about $34.39.
- Held to 20 years, the Treasury guarantee would make it worth at least $200 regardless of the rate path.
Result: About $134.39 after 10 years at a steady 3%.
Frequently asked questions
What is the EE doubling guarantee?
The Treasury guarantees a Series EE bond will be worth double its purchase price at 20 years, making a one-time adjustment if the fixed rate alone falls short. It is the main reason EE bonds reward very long holds.
How does the I bond rate work?
It combines a fixed rate (set at purchase, for the bond’s life) with an inflation rate that resets every May and November. Projecting today’s composite rate flat, as this calculator does, is a simplification.
Are there penalties for cashing in early?
Yes — bonds cannot be cashed in the first 12 months, and cashing before 5 years forfeits the last 3 months of interest. This projection does not apply those penalties.
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