Simple Interest Calculator Project (code) in Python

Simple Interest Calculator in Python.

About the project: This will be a self-contained script that calculates simple interest based on the principal amount, interest rate, and time period.

It will run in a continuous loop, so you can perform multiple conversions without restarting the program.

This script provides a user-friendly interface to calculate simple interest.

How to use this Simple Interest Calculator:

Run the Python script.
When you run it, It prompts you for the principal amount, interest rate, and time period,
then outputs a summary of the results.
You can perform multiple calculations in the same session.

Project Level: Beginner

You can directly copy the below snippet code with the help of green copy button, paste it and run it in any Python editor you have.

Steps: Follow these steps

Step 1: Copy below code using green 'copy' button.

Step 2: Paste the code on your chosen editor.

Step 3: Save the code with filename and .py extention.

Step 4: Run (Press F5 if using python IDLE)



# simple_interest_calculator.py

def get_numeric_input(prompt, min_value=0):
    """
    Helper function to get valid numeric input from the user.
    Ensures the input is a positive number.
    """
    while True:
        try:
            value = float(input(prompt).strip())
            if value <= min_value:
                print("Please enter a positive value.")
            else:
                return value
        except ValueError:
            print("Invalid input. Please enter a number.")

def calculate_simple_interest(principal, rate, time):
    """
    Calculates the simple interest and the total amount.
    
    Formula: Simple Interest = (Principal * Rate * Time) / 100
    
    Args:
        principal (float): The initial amount of money.
        rate (float): The annual interest rate (in percent).
        time (float): The time the money is invested or borrowed for (in years).
        
    Returns:
        tuple: A tuple containing the calculated simple interest and the total amount.
    """
    interest = (principal * rate * time) / 100
    total_amount = principal + interest
    return interest, total_amount

def main():
    """
    Main function to run the Simple Interest Calculator in a continuous loop.
    """
    print("--- Python Simple Interest Calculator ---")
    print("Enter 'q' at any time to quit.")
    
    while True:
        try:
            principal = get_numeric_input("Enter the principal amount: ")
            rate = get_numeric_input("Enter the annual interest rate (%): ")
            time = get_numeric_input("Enter the time in years: ")
            
            interest, total = calculate_simple_interest(principal, rate, time)
            
            print("\n--- Calculation Summary ---")
            print(f"Principal Amount: ${principal:.2f}")
            print(f"Annual Rate: {rate}%")
            print(f"Time Period: {time} years")
            print(f"Simple Interest: ${interest:.2f}")
            print(f"Total Amount: ${total:.2f}")
            print("---------------------------\n")
            
            play_again = input("Do you want to perform another calculation? (yes/no): ").strip().lower()
            if play_again != 'yes':
                print("Exiting Simple Interest Calculator. Goodbye!")
                break
        
        except ValueError:
            print("Invalid input. Please enter a valid number.")

# This ensures that main() is called only when the script is executed directly.
if __name__ == "__main__":
    main()