Series I Bond Calculator

Series I bonds (sold since September 1998) are bought at face value and grow with a composite rate: a fixed rate set for the bond's life plus an inflation adjustment that resets every May and November. That makes their value path hard to compute by hand — the Treasury's published tables are the only authoritative source, and that's what the calculator reads.

How I bond values move

• Rates reset semiannually: your bond's rate changes on its own 6-month anniversary schedule, not on the calendar reset — a common source of confusion the tables resolve exactly.
• 3-month penalty under 5 years: values shown for bonds younger than 5 years already exclude the last 3 months of interest, exactly what your bank would pay today.
• 12-month lockup: I bonds can't be cashed at all in the first year (the calculator will tell you when yours becomes redeemable).
• 30-year life: after final maturity the bond stops earning — the 2028-2029 wave of maturing 1998-99 I bonds is coming.

Paper I bonds from tax refunds

Millions of paper I bonds were issued through the IRS tax-refund program (2010–2024, denominations $50 to $5,000). They work the same as any I bond — pick "Series I", the printed denomination and the issue date, and you'll get the exact redemption value. Keep the whole stack organized in the private inventory.

High-inflation vintages are worth checking

I bonds bought in 2021–2022 rode record 7.12% and 9.62% inflation rates; many holders don't realize how much they've grown — or that rates have since fallen, which changes the hold-or-cash math. See today's exact value first, then decide.

The composite rate, in plain terms

An I bond's return has two moving parts. The fixed rate is set the month you buy and never changes for the life of that bond. The inflation rate resets every May and November based on CPI-U and applies to every I bond outstanding, regardless of when it was issued. The two combine into a composite rate that compounds semiannually — which is why two I bonds bought a year apart, at different fixed rates, can grow at noticeably different long-run paces even though they share the same inflation adjustment going forward. See how savings bond interest works for the general mechanics.

Purchase limits

TreasuryDirect currently caps electronic I bond purchases per person per calendar year; the paper I bonds issued through the IRS tax-refund program carried their own separate annual cap. Limits have changed over the program's history, so treat any specific number as a starting point to verify on treasurydirect.gov rather than a fixed rule — it isn't relevant to valuing a bond you already own, only to buying new ones.

EE vs. I: which one is this?

If you're holding a mixed stack and aren't sure which series a given bond is, the printed "Series I" or "Series EE" label on the certificate settles it immediately — the two series price and grow differently enough that guessing wrong will give you the wrong value. See the full EE vs. I comparison if you're deciding which to hold or which is which.

FAQs

Do I bonds ever lose value? No — the composite rate can't go below zero, so a redeemed I bond is never worth less than what you paid for it (before the 3-month penalty on early redemptions).

Is I bond interest taxable? Yes, federally, in the year cashed or at final maturity — see the tax guide.

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