The basic formula: original price plus accrued interest

A savings bond's current value is what you paid for it plus the interest it has earned since you bought it. That is the entire calculation. You do not need to know the final maturity value or the interest rate schedule — you only need three pieces of information: the purchase price, the current month and year, and the bond's series and issue date.

The U.S. Department of the Treasury publishes the exact interest rates that apply to every bond series and issue month. Once you know your bond's series (Series EE or Series I, most commonly) and the month you bought it, you can find the rate that applies to your specific bond. Then you multiply that rate by how many months have passed since purchase, and add the result to what you paid.

For most people, the easiest method is to use the Treasury's online calculator rather than doing the math by hand. But understanding what the calculator is doing — and why the number changes month to month — helps you know whether the result makes sense.

Key Takeaways

  • A savings bond's value equals its purchase price plus interest earned, and the interest rate depends on the bond's series and the month you bought it.
  • The Treasury publishes historical interest rates for every bond series and issue month on its website, so you can look up the exact rate that applies to your bond.
  • Series EE bonds earn interest monthly, and you can calculate the current value by multiplying the monthly rate by the number of months held, then adding that to the purchase price.
  • Series I bonds earn interest in two parts — a fixed rate that never changes, plus an inflation rate that adjusts every six months — so their value calculation is more complex but follows the same basic formula.
  • The Treasury's online savings bond calculator does this math for you if you enter your bond's series, issue date, and denomination, and it updates whenever new interest rates take effect.

Where to find the interest rate for your bond

The Treasury maintains a complete historical record of interest rates for Series EE and Series I bonds, organized by issue month and year. You can find this on the Treasury Direct website under "Historical Rates and Terms." The page lists every month going back decades, so even if your bond is very old, the rate that applies to it is there.

When you look up your bond's rate, you are finding the rate that was in effect during the month you purchased it. That rate stays locked in for the life of the bond — it does not change. What changes is how much interest has accumulated, because interest compounds monthly.

For Series EE bonds, the rate is straightforward: a single annual percentage rate. For Series I bonds, the rate has two parts. The fixed rate (which never changes) is listed separately from the inflation rate (which adjusts every May and November). You need both numbers to calculate an I bond's current value.

Calculating a Series EE bond's current value

Series EE bonds are the simpler calculation. Start with the purchase price — for most EE bonds sold after 2003, you paid half the face value. So a $100 face value bond cost you $50. That $50 is your starting point.

Next, find the annual interest rate that was in effect when you bought the bond. Let's say it was 1.10% per year. Divide that by 12 to get the monthly rate: 1.10% ÷ 12 = 0.0917% per month. Then count how many months have passed since the issue date. If your bond was issued in January 2020 and it is now January 2024, that is 48 months.

Multiply the monthly rate by the number of months: 0.0917% × 48 = 4.40%. Then multiply that percentage by the purchase price: 4.40% × $50 = $2.20. Add that to the purchase price: $50 + $2.20 = $52.20. That is your bond's current value.

The calculation assumes the bond has been held the entire time and no interest has been withdrawn. If you have cashed in part of the bond, the remaining value is lower.

Calculating a Series I bond's current value

Series I bonds are more complex because the interest rate has two components. The fixed rate stays the same for the life of the bond. The inflation rate changes every six months — on May 1 and November 1 — based on the Consumer Price Index.

To calculate an I bond's current value, you need to know which inflation rates have been in effect since you bought it. If you purchased the bond in March 2022, you would use the inflation rate that was in effect from May 2021 to October 2021 (the rate in effect when you bought it), then add the rates for each subsequent six-month period up to today.

The Treasury's website lists the composite rates (fixed rate plus inflation rate combined) for every six-month period. It is easier to use those composite rates than to add the fixed and inflation rates yourself. Find the composite rate for the period when you bought the bond, then find the composite rate for each six-month period since then. Add all of those rates together, divide by the number of six-month periods, and multiply by the purchase price.

Because the inflation rate adjusts twice a year, an I bond's value can jump noticeably on May 1 and November 1 each year. The fixed rate never changes, but the total interest you earn can vary significantly depending on inflation.

Using the Treasury's online calculator

The Treasury Direct website includes a free savings bond calculator that does all of this math for you. You enter the bond's series (EE or I), the face value or denomination, the month and year it was issued, and the current month and year. The calculator returns the current value instantly.

The calculator is updated whenever new interest rates take effect — on the first of each month for Series EE bonds, and on May 1 and November 1 for Series I bonds. If you run the calculation on the same day the rates change, you will see the new value reflected immediately.

The calculator works for bonds issued at any time in the past. It also works if you have already cashed in part of a bond — you enter the remaining denomination rather than the original one.

Why the value changes every month

A savings bond's value increases every single month, even though the interest rate itself does not change. This is because interest compounds monthly. Each month, you earn interest not just on the original purchase price, but also on all the interest that has accumulated so far.

For Series EE bonds, this compounding is automatic and happens behind the scenes. You do not have to do anything. The value simply grows month by month according to the rate that was locked in when you bought it.

For Series I bonds, the value jumps twice a year when the inflation rate adjusts. Between those adjustment dates, the value grows steadily as the fixed rate compounds monthly. On May 1 and November 1, the new inflation rate takes effect, and the total monthly growth may increase or decrease depending on whether inflation has gone up or down.

What happens after a bond reaches final maturity

Series EE bonds stop earning interest 30 years after they are issued. Series I bonds stop earning interest 30 years after they are issued as well. After that date, the value is fixed — it will not grow any further, even if you keep holding the bond.

You can cash in a bond at any time after you have held it for one year. If you cash it in within the first five years, you lose the last three months of interest as a penalty. After five years, there is no penalty.

If you hold a bond past its final maturity date without cashing it in, it simply sits at its final value. There is no benefit to holding it longer, so most people cash in mature bonds and reinvest the money elsewhere.

Frequently Asked Questions

Can I calculate my bond's value without knowing the exact purchase date?

You need at least the month and year. If you have the bond certificate itself, the issue date is printed on it. If you bought the bond through Treasury Direct online, you can log into your account and see the exact purchase date for every bond you own. Without the issue date, you cannot calculate the value accurately.

What if I bought my bond before 2003, when the purchase price was different?

Older Series EE bonds were sold at face value, not at half face value. So a $100 bond cost $100, not $50. The interest rate calculation is the same — you still look up the rate for the month you bought it and multiply by the number of months held — but your starting purchase price is different. The Treasury's historical rates page covers bonds going back to 1941.

Does the value change if I move the bond to a different account or person?

No. A bond's value depends only on its series, issue date, and how long it has been held. Moving it to a different account, transferring ownership, or changing the registration does not affect the value. The interest continues to accrue at the same rate.

Why is my bond worth less than the final maturity value listed online?

The final maturity value is what the bond will be worth 30 years after it was issued, assuming it earns interest the entire time. If your bond has not been held for 30 years yet, its current value will be lower. The final maturity value is a target, not the current value.

Can I use last month's interest rate to calculate this month's value?

No. The interest rate for a Series EE bond is set when you buy it and never changes. You must use the rate from the month you purchased the bond, not the current month's rate. For Series I bonds, you must account for every six-month inflation adjustment since purchase, not just the most recent one.