About this simple interest calculator
Calculate simple interest from a principal amount, annual rate, and time period.
How to use it
Enter the values requested by the calculator. Results update in your browser as you change the inputs. Review the assumptions shown on the calculator before using the result.
Formula
interest = P × r × t
Example
Use this when interest is calculated only on the original principal rather than on previously earned interest.
Frequently asked questions
What does the simple interest calculator show?
Calculate simple interest from a principal amount, annual rate, and time period.
Are the results exact?
The result is calculated from the inputs and assumptions shown on this page. For important financial, health, tax, or legal decisions, verify the result with an appropriate professional or authoritative source.