I Bond Treasury Rate Calculator
Calculate the composite yield of a U.S. Series I Savings Bond. The Treasury Department combines a fixed rate that lasts the bond's life with an inflation rate that resets every 6 months.
Year-by-Year Projection
The I Bond Treasury Rate Calculator is a free, browser-based tool that turns a Series I savings bond's fixed rate and semiannual inflation rate into its composite rate and projected value. It applies the official Treasury formula, including the 0% composite floor, so you can compare an existing bond against the current issue in seconds.
How Series I Savings Bonds Work
Series I Savings Bonds are inflation-protected U.S. government savings bonds. The Treasury Department combines two rates to determine your yield: a fixed rate that stays the same for the entire 30-year life of the bond, and an inflation rate that resets every 6 months on May 1 and November 1 based on the Consumer Price Index for All Urban Consumers (CPI-U). The composite rate formula is: Composite = Fixed + (2 × Inflation) + (Fixed × Inflation), with a 0% floor on the composite rate (source: TreasuryDirect I bond interest rates).
2026 I Bond Rate History and Outlook
I Bonds reached a peak composite rate of 9.62% in May 2022 due to high inflation, dropping to roughly 4.0-5.3% in 2024 as inflation cooled. The November 2024 issue had a 1.20% fixed rate plus 2.96% inflation rate, for a composite of 5.20%. The May 2025 fixed rate dropped to 1.10%. The current issue, covering purchases from 1 May 2026 through 31 October 2026, pays a 0.90% fixed rate and a 1.67% semiannual inflation rate for a 4.26% composite rate (source: TreasuryDirect I bond interest rates, checked 2026-08-12). The fixed rate is the most valuable component because it persists for the full 30 years, and at 0.90% it sits below the 1.10–1.30% locked in by 2024 and 2025 buyers — if you already hold an older bond, its fixed rate is better than anything on sale today, which is an argument for holding rather than redeeming and rebuying. The next reset takes effect 1 November 2026.
Should You Redeem an Old I Bond and Rebuy at Today's Fixed Rate?
This is the question the rate history above actually raises, and the arithmetic is simpler than it looks because only one of the two components is worth comparing. The inflation half is identical on every I Bond in existence — it resets to the same figure for everyone each May and November — so swapping bonds gains you nothing there. All that changes is the fixed rate, which is locked to the bond for its full 30 years. Today's issue carries a 0.90% fixed rate. Bonds bought in 2024 and 2025 locked 1.10% to 1.30%. Rebuying therefore lowers your permanent yield by 0.2 to 0.4 percentage points, and on top of that you pay two costs: the accrued interest becomes federally taxable in the year you redeem, and the new bond restarts both the 12-month lockout and the 5-year early-redemption penalty window. The trade only makes sense in reverse — when the fixed rate on offer is materially higher than the one on a bond you already hold, which was the case for anyone holding a 0.00% fixed-rate 2021 or 2022 bond when the fixed rate later climbed above 1%. Two practical checks before you act. First, look up your own bond's fixed rate rather than its headline composite, because the composite you see today tells you nothing about what you locked in. Second, if the bond is under five years old, run the three-month interest forfeit through the calculator above before assuming a swap is free. Rates and the reset schedule are published by TreasuryDirect. Updated 2026-08-20.
I Bond Tax Advantages
I Bonds enjoy three tax breaks. First, federal tax deferral: you don't pay taxes on accrued interest until you redeem the bond (or it matures at 30 years). Second, no state or local income tax — significant for residents of California, New York, New Jersey, Oregon, Hawaii, and other high-tax states. Third, the Education Tax Exclusion: if you use I Bond proceeds to pay qualified education expenses for yourself, your spouse, or your dependent, the interest may be entirely tax-free, subject to modified adjusted gross income phaseouts. The most recent figures published by the IRS are for tax year 2025: the exclusion phases out between $99,500 and $114,500 of MAGI for single filers, and between $149,250 and $179,250 for married filing jointly, disappearing entirely above the top of each band (source: IRS Publication 970). The IRS indexes these bands annually, so confirm the current-year figures before relying on the exclusion. Note also that the bond must be registered in the parent's name, not the child's, for the exclusion to apply. This makes I Bonds particularly powerful for college savings (see also IRS Publication 550).
I Bond Limits and Redemption Rules
Each individual can purchase $10,000 in electronic I Bonds per calendar year through TreasuryDirect, Paper I Bonds bought with a federal tax refund are no longer available — the IRS withdrew that option from 1 January 2025, so every I Bond issued since is electronic. Married couples and businesses with separate EINs can still effectively double or triple the limit. You cannot redeem an I Bond in the first 12 months. Redeeming between months 12-60 forfeits the most recent 3 months of interest. After 5 years, redemption is penalty-free. Bonds stop earning interest after 30 years. Strategy: even if you plan to hold long-term, don't put more than 10% of liquid assets into I Bonds because of the 1-year lockout. Last updated: 2026-08-20.
Frequently Asked Questions
What is the current I Bond rate in 2026?
I Bonds issued 1 May 2026 through 31 October 2026 carry a 0.90% fixed rate and a 1.67% semiannual inflation rate, for a 4.26% composite rate. The fixed 0.90% is locked for the full 30 years; the inflation half resets every May 1 and Nov 1 on CPI-U. Check TreasuryDirect.gov before purchasing, as the next reset lands 1 November 2026.
How is the I Bond composite rate calculated?
Composite = Fixed Rate + (2 × Semi-Annual Inflation Rate) + (Fixed Rate × Semi-Annual Inflation Rate). The composite rate has a 0% floor — it cannot go negative even if deflation occurs.
Can I buy more than $10,000 in I Bonds per year?
Yes, with planning. The $10,000 electronic limit is per Social Security Number. You can buy as gifts for family members (held in your account, delivered later), as a trust, and in a business name with its own EIN — potentially $30,000+ per couple per year. The old paper-bond route using up to $5,000 of a tax refund ended on 1 January 2025 and is no longer an option.
When can I redeem an I Bond?
You cannot redeem in the first 12 months at all. Months 12-60: redeemable but forfeit the most recent 3 months of interest. After 60 months: redeemable with no penalty. Bonds stop earning interest after 30 years.
Are I Bonds taxable?
Federal income tax applies but is deferred until redemption (or 30 years). No state or local tax. If used for qualified higher education, interest may be entirely tax-free under the Education Tax Exclusion (subject to income limits).
I Bond vs TIPS — which is better?
I Bonds: $10K/year limit, 1-year lockout, federal tax deferred, no state tax, fixed + inflation. TIPS: unlimited purchase, fully liquid, taxable each year, fixed + inflation. For most retail investors, I Bonds are simpler and more tax-efficient. TIPS are better for large amounts.
What's the difference between Series I and Series EE bonds?
Series EE: fixed rate at issue, doubles in value at 20 years (effective ~3.5% yield). Series I: variable composite rate tied to inflation. I Bonds are usually better when expected inflation exceeds ~1.5%, which has been almost always for the last 20 years.