Series I savings bonds · redemption timing
When should you cash out your I bond?
Enter the month your bond was issued and what you paid to get its rate history, an estimated value, the 3-month early-withdrawal penalty, and the best month to redeem so the penalty falls on your lowest-rate months — all in your browser.
Open the calculator ↗One date in, the whole timing picture out
When a rate drop is coming, it points to the exact month to redeem so the penalty forfeits the cheap months, not the expensive ones.
Redeem before 5 years and you give back the last 3 months of interest — see the estimate and the date it ends.
Your composite rate now and at the next 6-month anniversary (or “not yet announced”).
The 12-month lock, the 5-year penalty-end, and 30-year final maturity, from your issue month.
Why timing matters
An I bond's penalty is always the most recent 3 months of interest, and its rate changes every 6 months. So the month you redeem decides whether you forfeit high-rate or low-rate interest. ibondrate uses the official Treasury fixed-rate and semiannual-inflation tables and the published composite-rate formula — no black-box score — and runs entirely client-side, so nothing you enter is uploaded. Dollar figures are estimates; rates and dates are exact. Informational only — not financial advice.
Frequently asked questions
What does ibondrate do?
You enter the month a US Series I savings bond was issued and how much you paid. It works out the bond's exact rate history, an estimate of what it is worth today, the 3-month early-withdrawal penalty if you cash out before 5 years, and — the part most pages only describe in prose — the best month to redeem so that penalty falls on the lowest-rate months. Everything runs in your browser.
When can I cash an I bond, and what is the penalty?
You cannot redeem at all in the first 12 months. From month 12 through the end of year 5, redeeming costs you the most recent 3 months of interest. From 5 years onward there is no penalty and you keep every cent. The bond stops earning at 30 years. ibondrate shows the exact dates for all of these from your issue month.
When is the best time to cash out an I bond?
Two rules. First, interest is added on the 1st of each month and the value does not change until then, so redeem on the 1st (or the first business day after) — waiting until later in the same month gains nothing. Second, because the penalty is always the last 3 months of interest, if your rate is about to drop you usually do better holding until you are 3 months into the new, lower rate, so the penalty eats the cheap months instead of the expensive ones. ibondrate computes the specific month for your bond.
How is the composite rate calculated?
An I bond combines a fixed rate (set when you buy and fixed for the life of the bond) with a semiannual inflation rate (reset every May 1 and Nov 1). The composite annual rate = fixed + (2 × semiannual inflation) + (fixed × semiannual inflation ÷ 100), then floored at 0% so the bond never loses value. Your bond's rate changes every 6 months on its own issue-month anniversary, using whichever inflation rate was in effect when that 6-month period began.
Is the dollar value exact?
The rates, dates and timing are exact. The dollar value and penalty are close estimates: they use the published composite-rate method and monthly compounding, but Treasury rounds to the penny on a per-$25 basis with its own conventions. For the official figure to the cent, use the TreasuryDirect savings-bond value lookup or your TreasuryDirect account. ibondrate is for planning the timing, not for filing.
Where does the rate data come from?
The fixed-rate and semiannual-inflation tables come from the U.S. Treasury "Fiscal Data" I Bonds Interest Rates dataset and are cross-checked against the official TreasuryDirect rate announcements. The most recent period covered is May 2026 (0.90% fixed, 1.67% semiannual inflation, 4.26% composite). Rates beginning after the latest announcement are shown as "not yet announced".
Is this financial advice?
No. ibondrate is an informational calculator that does arithmetic on published Treasury rates — like a tax or mortgage calculator. It does not know your tax situation, goals, or other holdings and does not tell you whether to buy, hold, or sell. For decisions about your money, confirm figures on TreasuryDirect and consider talking to a licensed professional.
Is my data private?
Yes. This is a static page and every calculation happens in your browser with JavaScript. Your issue date and amount are never sent to a server, there is no backend, and nothing is logged.