Reviewed by Amy Drury What Is Compound Interest? Compound interest is interest that's calculated on both the initial principal of a deposit or loan and on all accumulated interest. It's a tremendous ...

Compound interest can help turbocharge your savings and investments, or it can quickly lead to an unruly balance, keeping you stuck in a cycle of debt. Its magic can help you earn more — or owe more.

Unless you're independently wealthy, you should be saving and investing for retirement ‒ starting, ideally, in your 20s or 30s. Sure, if you're 47 and haven't really started yet, start now. But those ...