Certificate of Deposit (CD) Calculator models guaranteed compound interest earnings, maturity values, and early withdrawal penalty thresholds for bank CDs and credit union share certificates.

### CD Compound Interest Mathematics Fixed-term certificates of deposit compound interest over an agreed duration: - **Maturity Balance Formula:** $$\text{Maturity Balance} = \text{Deposit} \times \left(1 + \frac{\text{APY}}{100}\right)^{\frac{\text{Term Months}}{12}}$ - **Total Interest Earned:** $$\text{Total Interest} = \text{Maturity Balance} - \text{Initial Deposit}$ - **Early Withdrawal Penalties:** Banks typically assess a 3-month simple interest penalty if funds are liquidated prior to the maturity date: $$\text{Penalty (3 Months)} = \text{Deposit} \times \left(\frac{\text{APY} / 100}{12}\right) \times 3$

### Worked Numeric Example Consider an individual investing $10,000 into a 12-month certificate of deposit at 4.80% APY: - **Deposit Amount:** $10,000 - **Term:** 12 months (1.0 year) - **APY:** 4.80% - **Final Maturity Balance:** $10,000 \times (1 + 0.0480)^1 = $10,480.00. - **Guaranteed Interest:** $10,480 - $10,000 = $480.00 ($40.00 monthly equivalent earnings). - **Early Withdrawal Penalty (3 Months):** ($10,000 \times 0.0480 / 12) \times 3 = $40.00 \times 3 = $120.00.

### In-Browser Calculation Note All interest compounding formulas run locally in browser JavaScript. No deposit amounts, bank balances, or personal financial figures are recorded or sent over the internet.