Compound Interest Explained
Compound interest means earning interest on money that already includes prior interest. In investing, returns may also compound when gains and income remain invested, but market returns are not fixed or guaranteed.
Why time changes the result
Compounding is nonlinear: later growth is based on a larger accumulated amount. Starting earlier can therefore matter even when contributions are modest.
For savings products with a stated rate, actual results depend on the rate, compounding schedule, fees and taxes. For investments, future returns are uncertain.
Nominal vs. effective rates
A nominal annual rate does not always show the full effect of compounding. An effective annual rate or APY-style measure incorporates compounding and can make product comparisons easier.
Use calculators as illustrations
A compound-growth calculator is useful for scenarios, but it should not be mistaken for a forecast. Test several rates and include fees or taxes where relevant.
A practical next step
Write down the one number or fact from this topic that affects your situation—such as a balance, rate, due date, fee, target amount or policy limit. Then verify any jurisdiction-specific rule with an official source before making a decision.