Python - Compound Interest GUI Calculator using Tkinter

Last Updated :15 Jul, 2025

Python offers multiple options for developing a GUI (Graphical User Interface). Out of all thePython GUI Libraries, Tkinter is the most commonly used method. In this article, we will learn how to create a Compound Interest GUI Calculator application usingTkinter.

Let’s create a GUI-based Compound Interest Calculator application.

Importing the module – Tkinter
Create the main window (container)
Add any number of widgets to the main window.
Apply the event Trigger on the widgets.

Below is what the GUI will look like:

Steps to Create Compound Interest GUI Calculator using Tkinter

Importing the`tkinter` Library:

 from tkinter import *

This imports all classes and functions from the tkinter library, which is used to create the GUI.

Function to Clear All Entry Fields

This function clears the content of all entry fields and sets the focus back to the principal_field.

Python

defclear_all():principal_field.delete(0,END)rate_field.delete(0,END)time_field.delete(0,END)compound_field.delete(0,END)principal_field.focus_set()

Function to Calculate Compound Interest:

This function retrieves values from the entry fields, calculates the compound interest, and inserts the result into the compound_field.

Python

defcalculate_ci():principal=int(principal_field.get())rate=float(rate_field.get())time=int(time_field.get())CI=principal*(pow((1+rate/100),time))compound_field.insert(10,CI)

Main Program:

This part initializes the main window of the GUI, sets the background color, window size, and title.

Python

if__name__=="__main__":root=Tk()root.configure(background='light green')root.geometry("400x250")root.title("Compound Interest Calculator")

Creating and Positioning Labels:

These lines create labels for the GUI and position them using the grid method.

Python

label1=Label(root,text="Principal Amount(Rs) : ",fg='black',bg='red')label2=Label(root,text="Rate(%) : ",fg='black',bg='red')label3=Label(root,text="Time(years) : ",fg='black',bg='red')label4=Label(root,text="Amount : ",fg='black',bg='red')label1.grid(row=1,column=0,padx=10,pady=10)label2.grid(row=2,column=0,padx=10,pady=10)label3.grid(row=3,column=0,padx=10,pady=10)label4.grid(row=5,column=0,padx=10,pady=10)

Creating and Positioning Entry Fields:

These lines create entry fields for user input and position them using the grid method.

Python

principal_field=Entry(root)rate_field=Entry(root)time_field=Entry(root)compound_field=Entry(root)principal_field.grid(row=1,column=1,padx=10,pady=10)rate_field.grid(row=2,column=1,padx=10,pady=10)time_field.grid(row=3,column=1,padx=10,pady=10)compound_field.grid(row=5,column=1,padx=10,pady=10)

Creating and Positioning Buttons:

These lines create buttons for submitting the form and clearing the fields, and position them using the grid method.

Python

button1=Button(root,text="Submit",bg="red",fg="black",command=calculate_ci)button2=Button(root,text="Clear",bg="red",fg="black",command=clear_all)button1.grid(row=4,column=1,pady=10)button2.grid(row=6,column=1,pady=10)

Starting the GUI Event Loop:

root.mainloop()

Complete Code

Python

# import all classes / functions from the tkinterfromtkinterimport*# Function for clearing the# contents of all entry boxesdefclear_all():# whole content of entry boxes is deletedprincipal_field.delete(0,END)rate_field.delete(0,END)time_field.delete(0,END)compound_field.delete(0,END)# set focus on the principal_field entry boxprincipal_field.focus_set()# Function to find compound interestdefcalculate_ci():# get a content from entry boxprincipal=int(principal_field.get())rate=float(rate_field.get())time=int(time_field.get())# Calculates compound interestCI=principal*(pow((1+rate/100),time))# insert method inserting the# value in the text entry box.compound_field.insert(10,CI)# Driver codeif__name__=="__main__":# Create a GUI windowroot=Tk()# Set the background colour of GUI windowroot.configure(background='light green')# Set the configuration of GUI windowroot.geometry("400x250")# set the name of tkinter GUI windowroot.title("Compound Interest Calculator")# Create a Principal Amount : labellabel1=Label(root,text="Principal Amount(Rs) : ",fg='black',bg='red')# Create a Rate : labellabel2=Label(root,text="Rate(%) : ",fg='black',bg='red')# Create a Time : labellabel3=Label(root,text="Time(years) : ",fg='black',bg='red')# Create a Compound Interest : labellabel4=Label(root,text="Amount : ",fg='black',bg='red')# grid method is used for placing# the widgets at respective positions# in table like structure .# padx keyword argument used to set padding along x-axis .# pady keyword argument used to set padding along y-axis .label1.grid(row=1,column=0,padx=10,pady=10)label2.grid(row=2,column=0,padx=10,pady=10)label3.grid(row=3,column=0,padx=10,pady=10)label4.grid(row=5,column=0,padx=10,pady=10)# Create a entry box# for filling or typing the information.principal_field=Entry(root)rate_field=Entry(root)time_field=Entry(root)compound_field=Entry(root)# grid method is used for placing# the widgets at respective positions# in table like structure .# padx keyword argument used to set padding along x-axis .# pady keyword argument used to set padding along y-axis .principal_field.grid(row=1,column=1,padx=10,pady=10)rate_field.grid(row=2,column=1,padx=10,pady=10)time_field.grid(row=3,column=1,padx=10,pady=10)compound_field.grid(row=5,column=1,padx=10,pady=10)# Create a Submit Button and attached# to calculate_ci functionbutton1=Button(root,text="Submit",bg="red",fg="black",command=calculate_ci)# Create a Clear Button and attached# to clear_all functionbutton2=Button(root,text="Clear",bg="red",fg="black",command=clear_all)button1.grid(row=4,column=1,pady=10)button2.grid(row=6,column=1,pady=10)# Start the GUIroot.mainloop()