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.

Interest can be charged when you borrow money or earned when you save. When you charge something on a credit card or take out a loan from a financial institution (student loan, auto loan, mortgage, ...