What is Simple Interest?

Simple interest is the most straightforward way to calculate how much interest a loan or deposit earns. You take the original amount (the principal), multiply it by the interest rate, and multiply again by the time period. That's it. Unlike compound interest, it doesn't snowball — interest is always calculated on the original principal, not on any interest that's already accumulated.

The Formula Explained

The formula is: SI = P × R × T, where:

• P is the Principal — the initial amount you're depositing or borrowing.
• R is the annual Rate of Interest, expressed as a decimal.
• T is the Time period in years.

The calculator handles the conversion from percentage to decimal and from months to years automatically, so you don't have to worry about that.

Why Use This Calculator?

• For short-term loans, simple interest gives you a quick ballpark for what you'll owe — before you commit to anything.
• If you've got money in a savings account that pays simple interest, you can see what it'll earn over a specific period.
• Students learning about interest for the first time will find simple interest much easier to grasp than compound interest, and working through a few examples here can make the concept click.
• The pie chart shows you what portion of your total amount is original principal versus earned interest — which is a much clearer picture than just a number on its own.