I Bond Rates by Period
What a Series I savings bond earns, period by period since 1998, with the composite rate worked from its two parts the way Treasury does it. The current period is May 2026 – October 2026.
An I bond bought between May 2026 and October 2026 earns 4.26% for its first six months: a fixed rate of 0.90% that it keeps for life, plus a semiannual inflation rate of 1.67% that resets every six months. Bonds bought earlier earn their own fixed rate with the same inflation rate; the last column shows each.
The May 2026 – October 2026 composite, worked
Treasury's formula: fixed rate + (2 × semiannual inflation rate) + (fixed rate × semiannual inflation rate), rounded to four decimals.
Every period since September 1998
"Composite at issue" is what bonds bought in that period earned for their first six months. "Earning now" is what those same bonds earn in the current period, with today's inflation rate applied to their own fixed rate.
Source: TreasuryDirect — I bonds interest rates. Fixed and inflation rates are as announced; every composite is recomputed with Treasury's formula and checked against Treasury's figure before publication. Rates are annual; the inflation rate is the semiannual figure Treasury publishes.
How I bond rates work
Treasury announces two numbers every May 1 and November 1. The fixed rate applies for the life of every bond issued in the following six months and never changes. The semiannual inflation rate is the change in the Consumer Price Index for all urban consumers (CPI-U) over the six months ending in the March or September before the announcement, and it applies to every outstanding I bond for the next six-month stretch of its own anniversary cycle. The composite combines them with the formula above, so a bond's earnings move with inflation but its fixed part is locked at purchase. Interest accrues monthly and compounds semiannually; a bond cashed before five years forfeits the last three months of interest, and cannot be cashed at all in its first twelve.
Sources: TreasuryDirect — I bonds interest rates (formula, fixed-rate and inflation-rate history) · TreasuryDirect — Series I earnings rate chart (every cohort's rate in every period) · 31 CFR Part 359
Informational only, not financial or tax advice. This page shows published rates and the arithmetic behind them; it does not say whether to buy, hold or redeem.
Last reviewed: May 2026 announcement · snapshot built 2026-10-26 from treasurydirect.gov · 57 periods on file.
Frequently asked questions
Does the composite rate I see today apply to a bond I bought years ago?
Only the inflation part does. Every I bond keeps the fixed rate it was issued with for its whole life, and takes the new inflation rate at its next six-month anniversary. So two bonds bought in different periods earn different composites in the same six months. The "Earning now" column shows each cohort's rate for the current period.
When does my bond's rate actually change?
Six months after its issue month, not on May 1 or November 1. A bond issued in March changes rate every September 1 and March 1, taking whatever inflation rate Treasury announced most recently before that date.
Can the composite rate go negative?
No. In a deflation period the inflation part can pull the composite below the fixed rate, but Treasury floors the composite at zero. That happened for the May 2009 and May 2015 periods, which the table shows with their negative inflation rates and the floor applied.
Where do these numbers come from?
TreasuryDirect's I bond rates page, which lists every fixed rate and inflation rate announced since September 1998. The composite on each page here is recomputed from those two figures with Treasury's published formula, and the check that runs before every deploy confirms it matches Treasury's own figure for every period.
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