Investing
Compound interest
Compound interest is the return generated on both the original principal and the interest already accumulated in prior periods.
Formula: Final balance = P0 × (1 + i)^n
Its effect grows exponentially over time: over long horizons, most of the final balance comes from interest rather than contributions.
It requires two conditions: reinvesting returns and not interrupting the process. Withdrawing money or pausing contributions resets a large part of the effect.