How To Build a Simple Interest Calculator Using Python

In this tutorial we will be building a simple simple interest calculator app using python, you can use it to calculate simple interest. Simple interest is an interest charge that borrowers pay to lenders for a loan.

To begin let’s first create a file called interest.py , inside the file let’s insert the code below.

class SimpleInterestCalculator:
    def __init__(self, principal, rate, time):
        self.principal = principal
        self.rate = rate
        self.time = time

    def calculateInterest(self):
        interest = (self.principal * self.rate * self.time) / 100
        return interest

In the code above we first begin by creating a class and then a function to calculate the interest. Next, we then create a loop that will ask the user for the principle, rate, and time until they choose to quit the program.

while True:
    try:
        principal = float(input("Enter the principal amount (or 0 to exit): "))
        
        if principal == 0:
            break

        rate = float(input("Enter the interest rate: "))
        time = float(input("Enter the time period (in years): "))

       
        calculator = SimpleInterestCalculator(principal, rate, time)

        interest = calculator.calculateInterest()

        
        print("Simple Interest: $",interest)
        print()

    except ValueError:
        print("Invalid input! Enter numeric values only.")
        print()

print("Exiting...")

Open your terminal and run the command python3 interest.py and you should see the calculator as shown below.