CalcKitSavings Bond Calculator
Your bond
Series I rates are the Treasury’s published rates: the composite rate changes every 6 months and this calculator applies each published rate in turn — it never assumes the first rate lasts. The Treasury has published rates only through Nov 2026, so for later periods it uses the assumed rate above (pre-filled with the Nov 2026 composite for your bond). This is an estimate, not your TreasuryDirect balance. Interest on savings bonds is exempt from state and local tax.
Example: a $1,000 Series I bond bought in January 2023 at 6.89% → about $1,125.83 by January 2026, with $125.83 of interest. The 6.89% rate applied only for the first 6 months; later periods earned 3.79%, 4.35%, 3.37%, 2.30% and 3.27%.
Behind the numbers
How a savings bond grows
A Series I bond earns a composite rate made of two parts: a fixed rate that stays with the bond for life, and an inflation rate that the Treasury resets every May 1 and November 1. The composite rate changes on each 6-month anniversary of the month you bought the bond, and interest compounds semiannually. That is why a bond bought at 6.89% does not keep earning 6.89%: after the first 6 months the rate follows the published inflation announcements. A Series EE bond is simpler — it earns one fixed rate set at purchase, and the Treasury guarantees it doubles in value after 20 years even if the fixed rate alone would not get it there. Both series mature after 30 years, cannot be cashed in during the first 12 months, and lose the last 3 months of interest if cashed in before 5 years.
Worked example: $1,000 Series I bought January 2023 (fixed rate 0.40%). The published composite rates were 6.89%, 3.79%, 4.35%, 3.37%, 2.30% and 3.27% for the six 6-month periods to January 2026. Value = $1,000 × 1.03445 × 1.01895 × 1.02175 × 1.01685 × 1.01150 × 1.01635 = $1,125.83, so interest earned is $125.83. Held only 3 years, cashing in costs the last 3 months of interest ($9.06), leaving $1,116.78.
The published rates
What the January 2023 bond actually earned
| 6-month period | Composite rate | Value at end of period |
|---|---|---|
| Jan 2023 – Jun 2023 | 6.89% | $1,034.45 |
| Jul 2023 – Dec 2023 | 3.79% | $1,054.05 |
| Jan 2024 – Jun 2024 | 4.35% | $1,076.98 |
| Jul 2024 – Dec 2024 | 3.37% | $1,095.13 |
| Jan 2025 – Jun 2025 | 2.30% | $1,107.72 |
| Jul 2025 – Dec 2025 | 3.27% | $1,125.83 |
Composite rates are the Treasury’s published rates, rounded to the nearest 0.01% as the Treasury publishes them. The fixed rate for bonds bought November 2022 to April 2023 was 0.40%.
Worked examples
Example bond values
| Bond | Held to | Value | Interest earned |
|---|---|---|---|
| $1,000 Series I, bought Jan 2023 | Jan 2026 (3 years) | $1,125.83 | $125.83 |
| $5,000 Series I, bought May 2023 | Nov 2025 (2.5 years) | $5,509.71 | $509.71 |
| $10,000 Series I, bought Nov 2022 | May 2026 (3.5 years) | $11,457.02 | $1,457.02 |
| $1,000 Series EE at 2.10%, bought Jan 2023 | Jan 2026 (3 years) | $1,064.68 | $64.68 |
| $2,500 Series EE at 2.70%, bought May 2025 | May 2027 (2 years) | $2,637.76 | $137.76 |
Tips before you cash in
Wait out the first 12 months: savings bonds cannot be redeemed at all in the first year, no matter the rate.
If you can, hold for 5 years. Cashing in earlier costs the last 3 months of interest — on the January 2023 example that is $9.06 on a $1,000 bond.
Do not judge an I bond by its first rate. The 6.89% headline lasted 6 months; the bond earned $125.83 over 3 years, not the $225-plus a flat 6.89% would suggest.
For EE bonds, the 20-year doubling guarantee is the real return: a $1,000 EE bond is worth $2,000 at 20 years even though 2.70% compounded alone would only reach about $1,709.82.
Good to know
Frequently asked questions
How does a Series I bond earn interest?
A Series I bond earns a composite rate: a fixed rate set when you buy it, plus an inflation rate the Treasury resets every May 1 and November 1. The composite rate changes on each 6-month anniversary of your purchase month, and interest compounds semiannually. The composite formula is fixed + (2 × semiannual inflation) + (fixed × inflation).
Why did my bond not earn 6.89% for 3 years?
The 6.89% composite rate applied only to the first 6 months of a bond bought between November 2022 and April 2023. After that the rate followed the published inflation announcements: 3.79%, then 4.35%, 3.37%, 2.30% and 3.27%. A $1,000 bond bought in January 2023 was worth $1,125.83 after 3 years, with $125.83 of interest.
When can I cash in a savings bond?
You cannot cash in a savings bond during the first 12 months. If you cash in before 5 years, you lose the last 3 months of interest: on the January 2023 example, redeeming in January 2026 gives $1,116.78 instead of $1,125.83. After 5 years there is no penalty, and bonds stop earning interest after 30 years.
What is the 20-year doubling guarantee on EE bonds?
The Treasury guarantees a Series EE bond will be worth twice its purchase price after 20 years, adding money at the 20-year mark if the fixed rate alone falls short. A $1,000 EE bond at 2.70% would compound to only about $1,709.82 in 20 years, so the guarantee adds about $290.18 to reach $2,000.