See what your Series I savings bonds are worth, the interest they've earned, and the 3-month penalty if you cash out before 5 years. ✓ TreasuryDirect rules
Value • Interest • Penalty
I bonds are inflation-protected US savings bonds. They earn a composite rate = a fixed rate (set at purchase, kept for the bond's life) plus a variable inflation rate that resets every six months. Interest compounds semiannually and is exempt from state and local tax. You can buy up to $10,000 per person per year electronically.
You can't redeem in the first 12 months, and if you cash out before 5 years you forfeit the last 3 months of interest. After 5 years there's no penalty. This calculator estimates value assuming a steady composite rate — your actual rate changes each six months. Estimate only, not investment advice.
US Series I savings bonds pay a composite rate combining a fixed rate, set at purchase and held for the life of the bond, with a variable inflation rate that resets every six months based on CPI-U. The combination is what makes them unusual: the fixed portion delivers a real return above inflation, while the variable portion guarantees purchasing power is preserved. The composite formula is not a simple sum — it includes a cross-product term. Practical constraints matter as much as the rate: $10,000 per person per year, no redemption in the first twelve months, and a three-month interest penalty before five years.
Composite rate = fixed + (2 × semiannual inflation) + (fixed × 2 × semiannual inflation)Interest compounds semiannuallyPenalty: last 3 months of interest forfeited if redeemed before 5 yearsLimit: $10,000 electronic per person per calendar yearwhere:
Assumptions: Federal tax applies on redemption but state and local tax never do. Interest can be deferred until redemption. The composite rate can fall to zero in deflation but never goes negative.
Compute the composite rate properly, including the cross-product term most people omit.
ResultA 4.54% composite rate — a real return of about 1.30%
The fixed rate is the only part that matters long-term, because the inflation component merely maintains purchasing power. A bond bought when the fixed rate is 1.3% keeps that real return for 30 years, which is why fixed-rate resets are worth timing purchases around.