Series I Savings Bonds Interest Rate Explained

Series I savings bonds earn a composite interest rate that combines a fixed rate, set when a bond is issued, with an inflation rate that changes every six months. The rate applying to a new bond depends on its issue date; check the U.S. Treasury’s current I bond rate announcement for the rate in effect now.

How the I bond rate is calculated

The composite rate is based on two components: the bond’s fixed rate and its semiannual inflation rate. The fixed rate remains part of the bond’s return for as long as that bond earns interest. The inflation component is recalculated every six months according to changes in the Consumer Price Index for All Urban Consumers (CPI-U).

The Treasury’s composite-rate formula is:

Composite rate = fixed rate + (2 × semiannual inflation rate) + (fixed rate × semiannual inflation rate)

Rates are expressed as decimals in the calculation. For example, a rate of 3.00% is 0.03. The result is then stated as an annual rate. The formula means that the fixed and inflation components interact; simply adding their displayed percentages can produce a slightly different result.

The semiannual inflation rate reflects the percentage change in CPI-U over a six-month measurement period. When the Treasury announces a new rate, it applies to bonds issued during the relevant six-month window. That rate is not a promise that the bond will earn the same rate forever.

Why the current rate depends on the issue date

I bond rates are announced twice a year, generally in May and November. The announced composite rate applies to bonds bought during the six months beginning on the announcement’s effective date. A bond’s issue date is the first day of the month in which it is purchased, rather than necessarily the day a buyer completes the transaction.

For an individual bond, its fixed rate is locked in at purchase, while its inflation rate resets every six months. As a result, two bonds owned by the same person can have different rates at the same time if they were issued in different periods. The rate shown in an announcement for newly issued bonds is therefore not necessarily the rate currently being earned by every outstanding I bond.

To find the applicable figures, use the Treasury’s rate information and identify the bond’s issue date. For a bond held in an online Treasury account, the account’s savings-bond details can also help show its issue date and value. A newspaper headline or an old search result may refer to a previous rate period.

How rate changes affect a bond

The inflation component changes every six months, but an owner’s reset dates are tied to the bond’s issue month. For example, a bond issued in March has rate periods that begin in March and September. The Treasury’s May announcement does not immediately reset every bond; it provides the rates that apply according to each bond’s schedule and the applicable inflation measurement.

The composite rate cannot fall below zero. If the inflation component is negative, the bond’s value does not decline because of a negative composite rate. However, a zero rate period does not erase interest earned in earlier periods. The fixed rate can be zero or positive, and it remains the same for that bond after purchase.

I bonds earn interest monthly, with interest compounded semiannually. The Treasury’s displayed value generally includes accrued interest subject to the early-redemption rules. The exact value on a particular date can depend on when interest is credited and whether a redemption penalty applies.

Holding period, access, and purchase limits

I bonds are designed as savings securities, not as a daily-access cash account. They must be held for at least 12 months before redemption. If redeemed before five years, the owner generally forfeits the most recent three months of interest. After five years, that early-redemption penalty no longer applies. Disaster-related exceptions may exist; consult Treasury guidance for the conditions.

Electronic I bonds can be purchased through TreasuryDirect, and paper I bonds are available only in limited circumstances, such as through an eligible federal tax refund. Purchase limits and transaction requirements can change, so check current Treasury instructions before buying. The rate alone does not describe liquidity, purchase limits, or the effect of redeeming early.

• Consider when the money may be needed: the one-year minimum holding period is important.
• Compare the bond’s fixed rate as well as its initial composite rate; the fixed component stays with the bond.
• Account for the three-month interest penalty that can apply to redemption before five years.
• Use the issue date to understand when the bond’s rate resets, rather than assuming every bond changes in May and November.

I bonds compared with inflation-protected alternatives

I bonds are U.S. savings bonds whose return changes with inflation, but they are not the only way to seek inflation protection. Treasury Inflation-Protected Securities (TIPS), for example, are marketable Treasury securities with principal adjustments linked to inflation. Their prices can change in the secondary market, so selling before maturity may result in a gain or loss. I bonds are not traded on an exchange, but they have their own holding restrictions and purchase limits.

Unlike a conventional fixed-rate savings bond, an I bond’s total return over time cannot be known from its initial composite rate alone. Future inflation resets are unknown, and a bond’s fixed rate depends on when it was issued. Comparing products therefore means looking at structure, access to funds, timing, and risks—not just a single advertised rate.

Frequently Asked Questions

What is the Series I savings bond interest rate right now?
The rate changes by issue period, and I can’t reliably state a live rate here. Check the U.S. Treasury’s latest I bond announcement, and confirm that its effective dates match the bond you plan to buy.

How often does the I bond interest rate change?
The Treasury announces new composite rates twice yearly, generally in May and November. An individual bond’s inflation component resets every six months according to its issue-month schedule; its fixed rate does not change.

Can an I bond lose value if inflation is negative?
A negative inflation component cannot make the composite rate negative, so the bond’s value does not decrease because of a negative rate. It may earn no interest during a period when the composite rate is zero.

Is the rate on a newly purchased I bond guaranteed for the life of the bond?
No. The fixed-rate component is set for that bond’s life, but its inflation component is recalculated every six months. The composite rate can therefore change over time.

When can I cash in an I bond?
In most cases, an I bond cannot be redeemed during its first 12 months. Cashing it in before five years generally costs the last three months of interest; Treasury rules and any exceptions should be checked before redemption.

What to check before relying on a rate

Use an official Treasury source for current rates, issue dates, purchase requirements, and redemption values. Be wary of pages that present a past rate as current or imply that a quoted composite rate is fixed for the entire holding period. For a specific bond, its issue date and fixed-rate component are as important as the latest inflation adjustment.

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