💵 Your I Bond Details
Min $25 electronic; max $10,000/person/year through TreasuryDirect
Enter purchase amount ($25-$10,000).
Select how long you plan to hold before redeeming
Select holding period.
0.90% for bonds bought Nov 2025-Apr 2026. Use 0 for 2020-2022 purchases.
Enter fixed rate (e.g. 0.90).
4.03% for Nov 2025-Apr 2026 period. Your bond uses rate from your issue-date anniversary.
Enter current composite rate.
Estimate for future periods. Used for multi-year projections.
Enter assumed future rate.
For estimated tax savings (state/local exempt; federal deferred)
Select tax bracket.
Redemption Value at 60 Months
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⚠️ Disclaimer: Future rate periods beyond the current composite rate are projected using your assumed future rate. Actual I bond values depend on inflation (CPI-U) rates set by the Treasury every May and November. For an exact current value, use TreasuryDirect.gov or the official Savings Bond Calculator at treasurydirect.gov/BC/SBCPrice. This calculator is for estimation and planning purposes only.
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Sources & Methodology
Composite rate formula from TreasuryDirect.gov official documentation. Current 4.03% rate confirmed November 1, 2025 (fixed 0.90% + semiannual inflation 1.56%). Semiannual compounding and 3-month penalty per TreasuryDirect Savings Bond Calculator methodology.
TreasuryDirect — I Bonds Interest Rates
Official source for current and historical I bond composite rates, fixed rates, and semiannual inflation rates. Confirms current composite rate of 4.03% (fixed 0.90% + semiannual inflation 1.56%) for bonds issued November 1, 2025 through April 30, 2026. Next rate announced May 1, 2026.
TreasuryDirect — I Bonds Overview & Rules
Official rules for purchase limits ($10,000/person/year electronic), minimum holding period (12 months), early redemption penalty (3 months interest for bonds under 5 years), and 30-year maximum maturity. Confirms semiannual compounding methodology and CPI-U rate determination process.
Official TreasuryDirect Composite Rate Formula:
Composite Rate = Fixed + (2 × Semiannual Inflation) + (Fixed × Semiannual Inflation)
Example: 0.0090 + (2 × 0.0156) + (0.0090 × 0.0156) = 0.0090 + 0.0312 + 0.0001404 = 0.0403 = 4.03%
Semiannual Compounding: Value after period = Prior Value × (1 + Composite Rate / 2)
3-Month Penalty (under 5 years): Value shown = Value after N periods − last 3 months of interest
Last 3 months = Value at (N-3 months) × (1 + rate/2)^0.5 − Value at (N-3 months)
Simplified: apply one less semiannual period and half of one more period for 3-month forfeit
After 5 years (60 months): No penalty, full compounded value.
Composite Rate = Fixed + (2 × Semiannual Inflation) + (Fixed × Semiannual Inflation)
Example: 0.0090 + (2 × 0.0156) + (0.0090 × 0.0156) = 0.0090 + 0.0312 + 0.0001404 = 0.0403 = 4.03%
Semiannual Compounding: Value after period = Prior Value × (1 + Composite Rate / 2)
3-Month Penalty (under 5 years): Value shown = Value after N periods − last 3 months of interest
Last 3 months = Value at (N-3 months) × (1 + rate/2)^0.5 − Value at (N-3 months)
Simplified: apply one less semiannual period and half of one more period for 3-month forfeit
After 5 years (60 months): No penalty, full compounded value.
Series I Bond Guide 2026: Rate, Formula, Rules & Strategy
Series I savings bonds (I bonds) are one of the most unique investment instruments issued by the U.S. Treasury. They are backed by the full faith and credit of the U.S. government, guaranteed to never lose value, exempt from state and local income taxes, and automatically adjust for inflation every 6 months. The current composite rate of 4.03% (November 2025 through April 2026) reflects a 0.90% fixed rate — one of the higher fixed rates in recent years — plus a 3.12% annualized inflation component.
The Official Composite Rate Formula
Composite Rate = Fixed + (2 × Semiannual Inflation) + (Fixed × Semiannual Inflation)
Source: TreasuryDirect.gov official documentation
Current example (Nov 2025-Apr 2026): Fixed = 0.90%, Semiannual Inflation = 1.56%
Composite = 0.0090 + (2 × 0.0156) + (0.0090 × 0.0156) = 0.0090 + 0.0312 + 0.0001404 = 4.03%
The formula's "(2 × semiannual)" converts the semiannual inflation rate to annual, and the "(Fixed × Inflation)" term accounts for semiannual compounding of the fixed component with the inflation component.
Current example (Nov 2025-Apr 2026): Fixed = 0.90%, Semiannual Inflation = 1.56%
Composite = 0.0090 + (2 × 0.0156) + (0.0090 × 0.0156) = 0.0090 + 0.0312 + 0.0001404 = 4.03%
The formula's "(2 × semiannual)" converts the semiannual inflation rate to annual, and the "(Fixed × Inflation)" term accounts for semiannual compounding of the fixed component with the inflation component.
Current I Bond Rate History (Recent Periods)
| Period | Fixed Rate | Semi. Inflation | Composite Rate |
|---|---|---|---|
| Nov 2025-Apr 2026 | 0.90% | 1.56% | 4.03% |
| May 2025-Oct 2025 | 1.10% | 1.43% | 3.98% |
| Nov 2024-Apr 2025 | 1.20% | 0.95% | 3.11% |
| May 2024-Oct 2024 | 1.30% | 1.48% | 4.28% |
| Nov 2022-Apr 2023 | 0.40% | 3.24% | 6.89% |
| May 2022-Oct 2022 | 0.00% | 4.81% | 9.62% |
Key Rules You Must Know
- Cannot redeem before 12 months — this is an absolute rule with no exceptions. Emergency funds must stay elsewhere.
- 3-month penalty before 5 years — redeeming between 12 and 60 months forfeits the last 3 months of interest. Still often worth it after 1-2 years at current rates.
- $10,000/person/year limit — electronic through TreasuryDirect.gov. Plus $5,000 paper via federal tax refund.
- Fixed rate locked at purchase — the 0.90% fixed rate for bonds bought Nov 2025-Apr 2026 is permanent for that bond's life. A higher future fixed rate would require buying new bonds.
- Never lose principal — if inflation goes negative, composite rate floors at 0%. Your bond only grows.
- Federal tax deferred — report interest in the year you redeem, or defer until 30-year maturity.
💡 Strategy tip: For optimal timing, buy at the end of any month — you earn the full month's interest regardless of purchase date. Redeem at the beginning of a month to ensure you receive credit for the completed period. Buying before April 30, 2026 locks in the current 0.90% fixed rate for the life of the bond — if May's rate has a lower fixed component, earlier buyers hold a permanent advantage.
Frequently Asked Questions
The current composite rate is 4.03% for bonds issued November 1, 2025 through April 30, 2026. This consists of a 0.90% fixed rate plus a 1.56% semiannual inflation rate (3.12% annualized). The next rate announcement is May 1, 2026, based on October 2025–March 2026 CPI-U data.
Official TreasuryDirect formula: Composite = Fixed + (2 × Semiannual Inflation) + (Fixed × Semiannual Inflation). For current period: 0.0090 + (2 × 0.0156) + (0.0090 × 0.0156) = 4.03%. The semiannual inflation rate is based on CPI-U changes over the preceding 6 months, set every May 1 and November 1.
Semiannually — twice per year on your bond's anniversary month. Every 6 months, interest earned is added to principal, and the next period's rate is applied to the new higher balance. Formula: New Value = Prior Value × (1 + Composite Rate / 2). At 4.03%, $10,000 grows to $10,201.50 after 6 months, then $10,407.07 after 12 months.
If you redeem before 5 years (60 months) of holding, you forfeit the last 3 months of interest. You cannot redeem at all before 12 months. After 5 years, no penalty applies. TreasuryDirect automatically shows values with the 3-month penalty already subtracted for bonds under 5 years old.
$10,000 per person per calendar year through TreasuryDirect (electronic). Plus $5,000 per person in paper bonds using your federal tax refund. Married couples can combine: $20,000 electronic + $10,000 paper = $30,000 per year. Trusts and entities have separate $10,000 limits.
I bond interest is exempt from all state and local income taxes. Federal income tax is deferred until you redeem (up to 30 years). If you use I bond proceeds for qualified higher education expenses, interest may be fully exempt from federal tax as well (income limits apply — check IRS Form 8815).
No. The composite rate floors at 0% — even in deflation, your bond will not decrease in value. Once interest is credited, it cannot be taken away. Principal is guaranteed by the full faith and credit of the U.S. government.
The fixed rate is permanently locked at your purchase date (0.90% for Nov 2025-Apr 2026 purchases). The semiannual inflation component resets every 6 months from your issue date — not calendar year. If you bought in March, your rate changes every March and September. The new inflation rate for each period is based on the preceding 6-month CPI-U change.
If the May 1 announcement reveals a higher fixed rate than 0.90%, buying after May 1 locks in a better permanent rate. If the fixed rate decreases, buying before April 30 at 0.90% is better. You cannot predict the fixed rate in advance — it is set by Treasury. The variable (inflation) component can be estimated from CPI data once March 2026 CPI is released (around April 10).
For electronic bonds: log into TreasuryDirect.gov, click Current Holdings, select a series, and click Submit. For paper bonds: use the official Savings Bond Calculator at treasurydirect.gov/BC/SBCPrice — enter your bond's series, denomination, serial number, and issue date. This calculator provides estimates using the official formula for planning purposes.
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