United States Savings Bonds Calculator
Estimate the growth and current value of your Series EE or Series I savings bonds.
Results Summary
Initial Investment:
Estimated Current Value:
Total Interest Earned:
Years Held:
Estimated Total Increase:
Understanding US Savings Bonds
United States Savings Bonds are debt securities issued by the U.S. Department of the Treasury to help pay for the government's borrowing needs. They are considered one of the safest investments because they are backed by the full faith and credit of the United States government.
Series I Savings Bonds
Series I bonds are non-marketable, interest-bearing securities. Their earnings rate is a combination of a fixed rate and a semiannual inflation rate. This protects the purchasing power of your investment. They earn interest for up to 30 years unless cashed in earlier.
Series EE Savings Bonds
Series EE bonds issued since May 2005 earn a fixed rate of interest. A unique feature of EE bonds is the Treasury's guarantee that the bond will double in value if held for 20 years. If the regular interest doesn't double the value, the Treasury makes a one-time adjustment to fulfill that guarantee.
How the Calculation Works
This calculator uses the standard compound interest formula for semiannual compounding, which is the method the Treasury uses for most savings bonds:
Formula: A = P(1 + r/n)^(nt)
- A: The amount of money accumulated after n years, including interest.
- P: The principal investment (purchase price).
- r: The annual interest rate (decimal).
- n: Number of times interest is compounded per year (2 for savings bonds).
- t: The number of years the money is invested.
Real-World Example
Imagine you purchased a Series I Bond in January 2015 for $1,000. If the average annual interest rate over that period was 4%, and you check the value in 2024 (9 years later):
- Initial Investment: $1,000
- Compounding: Semiannual (2 times/year)
- Total Periods: 18
- Estimated Value: $1,428.25
- Total Interest: $428.25
Important Limitations
Please note that this calculator provides an estimate. Actual savings bond values depend on specific rates set by the Treasury every May and November. For Series I bonds, the inflation component changes frequently. Additionally, if you cash in a bond held less than 5 years, you forfeit the last 3 months of interest.