I bond calculator: value, penalty and the best month to cash out
Two fields — the month the bond was issued and what you paid. Everything else is computed from the Treasury rate tables: the rate it is earning now, the rate it moves to next, what it is worth, what cashing it early costs, and which of the next eighteen months keeps the most.
Figures verified · next scheduled change (new fixed and inflation rates)
The figures behind this tool
| Figure | Value | Applies | Source |
|---|---|---|---|
| An I bond cannot be redeemed for the first 12 months after issue. | 12 months | long-standing | TreasuryDirect — I bonds |
| Redeeming before 5 years (months 12–59) forfeits the most recent three months of interest. | the last 3 months of interest | long-standing | TreasuryDirect — I bonds |
| An I bond stops earning interest 30 years after issue. | 30 years | long-standing | TreasuryDirect — I bonds |
| Minimum electronic I bond purchase; any amount above $25 to the penny. | $25 | long-standing | TreasuryDirect — I bonds |
| Electronic I bond purchase limit per Social Security or Employer Identification Number per calendar year. | $10,000 | long-standing | TreasuryDirect — I bonds |
| Treasury’s published composite-rate formula; reproduces the API’s combined_rate exactly. | fixed rate + 2 × semiannual inflation + (fixed × semiannual inflation ÷ 100), floored at 0% | long-standing | TreasuryDirect — how I bonds earn interest |
| Fixed and semiannual inflation rates for every six-month period since May 1998 | 4.26% now | 1998-09 → 2026-10 | The full series, with a CSV |
The calculator needs JavaScript. The figures in this table, the rate on the rate page and the whole rate history do not.
What this does not do
- It does not read your TreasuryDirect account. Nothing you type leaves the browser, so the amount you enter is what you paid — not a balance we can look up.
- It does not give a penny-exact value. Treasury rounds per $25 with its own conventions; every dollar figure here carries an estimate tag for that reason.
- It does not price a rate Treasury has not set. Periods past the latest announcement are drawn hatched and labelled, never filled in with a guess.
- It does not handle more than one bond at a time yet, and it does not compute the tax on your interest.
- It does not tell you whether to hold or sell. It shows what each month keeps; the decision is yours.
01In this section
Questions
When can I cash an I bond?
Not for the first 12 months after the issue month. From then until the end of year five, redeeming costs the last 3 months of interest. From five years onward there is no penalty at all, and the bond stops earning after 30 years. The calculator prints all three dates from your issue month.
How much is the early redemption penalty?
It is the last 3 months of interest — not a percentage of your money, and not a fixed fee. Because it is always the most recent three months, its size depends on which rate those three months were earning. The period ledger on this page marks exactly which months the penalty would take.
When is the best month to cash out an I bond?
Two rules decide it. Interest posts on the 1st of the month and the value does not move until then, so redeeming later in a month gains nothing. And because the penalty is always the last three months of interest, when a rate drop is ahead you usually keep more by holding until you are three months into the lower rate. The strip on this page ranks the next eighteen months for your bond.
Is the dollar value exact?
The rates, the dates and the timing are exact. The dollar amounts are estimates: they apply the published composite-rate method with semiannual compounding, while Treasury rounds to the penny on a per-$25 basis with its own conventions. For the official figure, use your TreasuryDirect account.
What happens when the next rate has not been announced?
The tool says so instead of guessing. Periods beyond the latest announcement are drawn hatched and labelled "not announced yet", and if your bond has already entered such a period no dollar figure is printed as firm — the value is stated through the last month Treasury has covered. The next announcement is November 1, 2026.
Sources
- TreasuryDirect — I bonds interest rates · accessed 2026-09-07
- Treasury Fiscal Data — I Bonds Interest Rates · accessed 2026-09-07
- TreasuryDirect — I bonds · accessed 2026-09-07
Also this year
Every 2026 threshold on one pagewith the source and the day we checked it→The money calendarnext: the November 1, 2026 rate announcement→Information, not advice. Confirm your bond’s rate and value in your TreasuryDirect account.