How Do Banks Calculate Interest on Savings Accounts?

You check your savings account every month, see a small deposit labeled “interest paid,” and wonder: how did the bank calculate that? Is it just your balance times the interest rate? Not exactly. Banks use specific methods, compounding frequencies, and formulas that can either work for you or against you — depending on how much you know.

In this complete 2026 guide, you’ll learn the exact math behind savings account interest, the difference between APR and APY, how daily balance vs. average daily balance changes your earnings, and — most importantly — how to make your money grow faster. Plus, we’ve included real-world examples, comparison tables, and free tools to calculate your own interest.