I Bond Interest Calculator

See accrued interest on a Series I savings bond.

Your I-bond numbers never leave your browser — all math runs locally.

Try: Purchase year=2023, Purchase amount=1000, Valuation year=2026, Valuation month=8 → 6.88%, 43, $1,274, $274, $22, $1,252

How to use

Enter the purchase year, amount and a valuation date. The calculator compounds semi-annually at the purchase-year composite rate.

I-bonds add interest monthly, compounded semi-annually, and it is reported when you redeem.

The fixed portion stays for the bond’s life; the inflation portion resets every six months.