Compound Interest: FV = P × (1 + r/n)^(n×t)

With Monthly Deposits: FV = P(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)] × (1+r/n)

APY Conversion: APY = (1 + r/n)^n − 1

After-Tax: Interest × (1 − Tax Rate)

Early Withdrawal Penalty: (Penalty Months / 12) × Principal × APR