Savings Bond Calculator

How this calculator works

U.S. savings bonds are issued by the Treasury and backed by the federal government. Interest compounds semiannually and is added to the bond's value every six months. You choose a bond type, enter the purchase amount and rate, and the calculator projects the redemption value year by year.

Series I vs. Series EE

• Series I bonds earn a composite rate made of a fixed rate (set when you buy, never changes) plus an inflation rate that resets every six months. The composite is: fixed rate + 2 × semiannual inflation + fixed rate × semiannual inflation. For I bonds issued May–October 2026 the fixed rate is 0.90% and the composite rate is 4.26%.
• Series EE bonds earn a fixed rate for their whole life. EE bonds issued May–October 2026 earn 2.40%. The Treasury also guarantees an EE bond will at least double in value after 20 years, which this calculator applies automatically.

Rules worth knowing

• You can't cash a bond in during its first 12 months.
• Cash out before 5 years and you lose the last 3 months of interest.
• Bonds earn interest for up to 30 years.
• The minimum purchase is $25, and each person can buy up to $10,000 of each type per calendar year electronically.
• Interest is exempt from state and local income tax and is federally taxable, either yearly or when you redeem.

About the estimate

Real I bond rates change every May and November, so no one can know the future composite rate. This calculator assumes the fixed and inflation rates you enter stay constant. Use it for planning, and confirm exact values on TreasuryDirect.gov.