I bond calculator
$10,000 of I bonds bought in October 2016 is worth $13,788.00 in October 2026, $3,788.00 of interest. Pick your bond's issue month to see yours.
Your bond
The issue date is on a paper bond and in your TreasuryDirect account. I bonds are sold at face value, so the amount paid is the face value.
Your $10,000 I bond from October 2016 in October 2026
Value with all interest
$13,788.00
Fixed rate 0.10% for the life of the bond
Interest earned
$3,788.00
120 months of interest
If you cash it in now
$13,788.00
Over 5 years old, so there is no penalty.
Rate history for this bond (20 six-month periods)
| Period | Fixed | Semiannual inflation | Composite (annual) |
|---|---|---|---|
| Apr 2026 to Sep 2026 | 0.10% | 1.56% | 3.22% |
| Oct 2025 to Mar 2026 | 0.10% | 1.43% | 2.96% |
| Apr 2025 to Sep 2025 | 0.10% | 0.95% | 2.00% |
| Oct 2024 to Mar 2025 | 0.10% | 1.48% | 3.06% |
| Apr 2024 to Sep 2024 | 0.10% | 1.97% | 4.04% |
| Oct 2023 to Mar 2024 | 0.10% | 1.69% | 3.48% |
| Apr 2023 to Sep 2023 | 0.10% | 3.24% | 6.58% |
| Oct 2022 to Mar 2023 | 0.10% | 4.81% | 9.72% |
| Apr 2022 to Sep 2022 | 0.10% | 3.56% | 7.22% |
| Oct 2021 to Mar 2022 | 0.10% | 1.77% | 3.64% |
| Apr 2021 to Sep 2021 | 0.10% | 0.84% | 1.78% |
| Oct 2020 to Mar 2021 | 0.10% | 0.53% | 1.16% |
| Apr 2020 to Sep 2020 | 0.10% | 1.01% | 2.12% |
| Oct 2019 to Mar 2020 | 0.10% | 0.70% | 1.50% |
| Apr 2019 to Sep 2019 | 0.10% | 1.16% | 2.42% |
| Oct 2018 to Mar 2019 | 0.10% | 1.11% | 2.32% |
| Apr 2018 to Sep 2018 | 0.10% | 1.24% | 2.58% |
| Oct 2017 to Mar 2018 | 0.10% | 0.98% | 2.06% |
| Apr 2017 to Sep 2017 | 0.10% | 1.38% | 2.86% |
| Oct 2016 to Mar 2017 | 0.10% | 0.08% | 0.26% |
November 2026 I bond rate
Treasury announces the new I bond fixed and inflation rates on November 1, 2026. The May 2026 rate was reported on April 30, a day early, so this page may fill in on October 31. Until the new rate is announced, there is no November rate to show, and nothing on this page forecasts it.
The current rate, for I bonds issued May 2026 through October 2026, is 4.26% composite with a 0.90% fixed rate (semiannual inflation 1.67%). Source: TreasuryDirect, May 1, 2026 rate announcement, and the I bonds interest rates page, read on October 27, 2026.
A bond bought in October keeps the 0.90% fixed rate for life and earns 4.26% for its first six months. Its second six months, from April 2027, use the inflation rate Treasury sets in November, which is not known yet. A bond bought in November gets the new fixed rate. When the rate is announced, this block shows the new composite and fixed rate, the change from May, and what $10,000 bought in October is worth against $10,000 bought in November.
How an I bond earns interest
Every I bond has two rates. The fixed rate is set when you buy and never changes. The inflation rate is reset every May 1 and November 1 from the CPI-U. Bonds bought from May 2026 through October 2026 have a 0.90% fixed rate and earn 4.26% for their first six months.
The two combine into one composite rate: fixed + 2 × semiannual inflation + fixed × semiannual inflation, rounded to 0.01%. Deflation can pull it below the fixed rate, but never below zero, so an I bond does not lose value. Your bond switches to a new rate every six months counted from its issue month, not on May 1 and November 1.
Interest is added on the first day of each month and compounds every six months. You can't cash an I bond in its first 12 months. Cash it before 5 years and you lose the last 3 months of interest. After 30 years it stops earning.
This page covers Series I bonds only. For paper EE or E bonds, use TreasuryDirect's Savings Bond Calculator.
Methodology and sources
Fixed and semiannual inflation rates for every issue window since September 1998 come from TreasuryDirect's I bonds interest rates page, read on October 27, 2026 and checked against its rate history spreadsheet. The latest rates are the ones set on May 1, 2026; values are shown for October 2026.
Values follow the rules in 31 CFR part 359: the value of a $25 unit is computed month by month and rounded to the cent, then scaled to your amount, as TreasuryDirect does. The calculation reproduces the worked examples in that regulation and TreasuryDirect's published composite rates. TreasuryDirect's own figures are final if they ever differ.
Interest is subject to federal income tax but not state or local tax; this calculator shows values before tax.
This calculator is an educational tool, not financial advice. It estimates values from public rates and does not know your bonds; check your TreasuryDirect account for the official value.