Simple Interest Calculator

Simple interest is the most basic form of interest calculation where interest is computed only on the original principal amount throughout the loan or investment period. The interest does not compound—each period's interest is based solely on the initial amount. While simple interest is less common in modern banking (most savings accounts and loans use compound interest), it still applies to certain financial products: short-term personal loans, some auto loans, bonds with fixed coupon payments, and certain types of treasury bills and notes. Understanding simple interest provides a foundation for grasping more complex financial concepts. The straightforward linear relationship between time, principal, and rate makes it easy to calculate returns or costs mentally in simple scenarios. Comparing simple interest to compound interest demonstrates why compound interest is often called "the eighth wonder of the world"—over long periods, the difference becomes dramatic as compound interest grows exponentially while simple interest grows linearly.