Savings Bond Calculator (I & EE Bonds)
Choose I or EE, enter your purchase amount and years held, and see the estimated value using the current Treasury rate.
US savings bonds earn interest that compounds semiannually. Series I bonds pay a composite rate that combines a fixed rate with inflation and resets every six months; Series EE bonds pay a fixed rate and are guaranteed to double in value if held 20 years. As of May–October 2026 the I bond composite rate is 4.26% and the EE rate is 2.40%.
⚠️ Double-check important results. This is an educational estimate, not professional advice — and where it uses a rate, bracket or fee, those change over time. Verify anything you'll rely on, especially in legal, financial, tax or medical matters, and read our full disclaimer. Think a result is wrong? Tell us so we can fix it.
How to Use This Calculator
Choose whether you hold a Series I or Series EE bond. Enter the amount you paid and how many years you plan to hold it. The rate field pre-fills with the current Treasury rate for that series — 4.26% for I bonds and 2.40% for EE bonds as of May–October 2026 — and switches automatically when you change the bond type. Overwrite it with a different rate to model a scenario.
The calculator estimates the bond's value with semiannual compounding. For EE bonds held to 20 years, it also applies the Treasury guarantee that the bond will have at least doubled.
How the Calculation Works
Savings bond interest compounds twice a year, so the annual rate is halved and applied over twice as many periods as years. That is the standard semiannual compounding formula.
Series I bonds are special because their composite rate changes every six months as inflation moves, so a projection over several years assumes today's rate holds — it usually will not. Series EE bonds carry a Treasury guarantee: if you hold one for 20 years, its value will have at least doubled, which can imply an effective rate higher than the stated one.
value = principal × (1 + rate ÷ 2)^(years × 2)
Worked Example
Take a $1,000 Series I bond at the current 4.26% composite rate, held for 5 years. The semiannual rate is 4.26 ÷ 2 = 2.13%, applied over 10 half-years: 1,000 × (1.0213)^10 ≈ $1,234.60, so about $234.60 of interest.
A $1,000 EE bond held the full 20 years is guaranteed to be worth at least $2,000 regardless of its lower stated rate — that doubling guarantee is the reason to hold EE bonds long term.
Assumptions, Limitations and Rate Source
This is an educational estimate. It assumes the rate you enter stays constant, but the I bond composite rate resets every six months, so real long-term I bond growth will differ as inflation changes. I bonds also cannot be cashed in the first 12 months, and redeeming before 5 years forfeits the last 3 months of interest.
For the exact value of a specific bond, use the Treasury's official Savings Bond Calculator. Rates are set by the U.S. Treasury and published on TreasuryDirect.
- Assumes a constant rate; the I bond composite rate resets every 6 months
- I bonds have a 1-year minimum hold; cashing before 5 years forfeits 3 months' interest
- EE bonds are guaranteed to double only if held the full 20 years
- For an exact figure, use the official TreasuryDirect Savings Bond Calculator
📊 Source & data. Formula and default values reference U.S. Treasury (TreasuryDirect) — Savings Bond Rates, May 2026. Last verified 2026-07-31. Rates, brackets and fees change over time — all editable fields accept your own current values.
Who Uses a Savings Bond Calculator
Savers and gift-givers use this to estimate how a US Series I or EE savings bond grows over time. Run it before buying to compare bonds against other safe savings, to plan for a goal like education or a gift, or to see roughly what an existing bond may be worth today. It puts the Treasury's current rates into a projected balance you can plan around.
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Open calculator →Frequently Asked Questions
What is the current I bond rate?
For I bonds issued May 1 to October 31, 2026, the composite rate is 4.26%, which includes a 0.90% fixed rate. The composite rate resets every six months based on inflation.
What is the current EE bond rate?
Series EE bonds issued May to October 2026 earn a fixed 2.40%. Separately, EE bonds are guaranteed by the Treasury to at least double in value if held for 20 years.
How often do savings bond rates change?
The Treasury sets new rates every May 1 and November 1. The I bond composite rate changes each period with inflation; the EE fixed rate applies for the life of bonds bought in that period.
How does the EE bond doubling guarantee work?
If you hold a Series EE bond for 20 years, the Treasury makes a one-time adjustment so it is worth at least twice what you paid, even if the stated interest alone would not get there.
Can I cash a savings bond anytime?
Not immediately. You must hold at least 12 months. If you redeem before 5 years, you forfeit the previous 3 months of interest. After 5 years there is no penalty.
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