Currency Exchange Rate Calculator GUI

Abstract

A currency converter is the perfect “small but real” beginner project: it has a user interface, talks to a live API on the internet, parses structured data (JSON), and produces output the user actually cares about. In this tutorial you will build a desktop GUI in Tkinter that lets the user type an amount, pick a source currency and a target currency from dropdowns, and click Convert to see today’s rate applied.

You will learn:

How to build a Tkinter window with labels, entries, dropdowns, and buttons.
How to call an HTTP API with requests and parse JSON responses.
How to handle network errors gracefully so the app never crashes mid-conversation.
How to organize widget-driven code with callbacks.
How to extend the converter into a tool you might actually use.

Prerequisites

Python 3.6 or above.
A text editor or IDE.
An internet connection.
Comfort installing packages with pip.
Familiarity with functions and conditionals.

Install Dependencies

install

pip install requests

tkinter ships with Python — no install needed.
requests is the de-facto library for HTTP in Python.

Pick an Exchange-Rate API

There are several free public APIs you can use without an API key:

API	URL pattern	Notes
exchangerate-api	`https://open.er-api.com/v6/latest/USD`	Free tier, no key, daily updates.
frankfurter.app	`https://api.frankfurter.app/latest?from=USD&to=EUR`	Open-source, ECB rates.
Fixer.io	`https://api.exchangerate.host/latest?base=USD`	Larger currency list.

For this tutorial we will use exchangerate.host (no key required). The response is JSON like:

json

{
  "base": "USD",
  "rates": { "EUR": 0.92, "GBP": 0.79, "INR": 83.10, ... }
}

💡 Any API can change its terms. If yours stops working, swap the URL — the parsing code is similar.

Getting Started

Create the project

Create a folder named currency-exchange-calculator.
Inside it, create currencyexchnageratecalculator.py.
Open the folder in your editor.

Write the code

Currency Exchange Rate Calculator GUI

pch.viewSource

Currency Exchange Rate Calculator GUI

# Currency Exchange Rate Calculator GUI

from tkinter import *
from tkinter import ttk
from tkinter import messagebox
import requests
import json

# Create an instance of tkinter frame
win = Tk()

# Set the geometry of tkinter frame
win.geometry("700x400")

# Set the title of tkinter frame
win.title("Currency Exchange Rate Calculator")

# Disable resizing the GUI by passing in False/False
win.resizable(False, False)

# Create a function to convert currency
def exchange():
    # Get the amount from the amount entry box
    amount = float(amount_entry.get())
    
    # Get the currency from the currency combobox
    currency = currency_combo.get()
    
    # Get the converted currency from the converted currency combobox
    converted_currency = converted_currency_combo.get()
    
    # Create a base URL
    base_url = "https://api.exchangerate-api.com/v4/latest/"
    
    # Create a full URL
    full_url = base_url + currency
    
    # Send a request to the URL
    response = requests.get(full_url)
    
    # Convert the response to JSON format
    response_json = response.json()
    
    # Get the currency rates from the response
    rates = response_json['rates']
    
    # Get the currency rate for the converted currency
    converted_currency_rate = rates[converted_currency]
    
    # Calculate the converted currency amount
    converted_currency_amount = converted_currency_rate * amount
    
    # Round the converted currency amount to 2 decimal places
    converted_currency_amount = round(converted_currency_amount, 2)
    
    # Create a message box to display the converted currency amount
    messagebox.showinfo("Converted Currency Amount", f"{converted_currency_amount} {converted_currency}")
    
# Create a function to clear the GUI
def clear():
    # Clear the amount entry box
    amount_entry.delete(0, END)
    
    # Clear the currency combobox
    currency_combo.set("")
    
    # Clear the converted currency combobox
    converted_currency_combo.set("")
    
# Create a function to exit the GUI
def exit():
    # Exit the GUI
    win.destroy()
    
# Create a label for the amount entry box
amount_label = Label(win, text="Amount:", font=("Arial", 10, "bold"))

# Create a label for the currency combobox
currency_label = Label(win, text="Currency:", font=("Arial", 10, "bold"))

# Create a label for the converted currency combobox
converted_currency_label = Label(win, text="Converted Currency:", font=("Arial", 10, "bold"))

# Create a label for the amount entry box
amount_label.place(x=30, y=50)

# Create a label for the currency combobox
currency_label.place(x=30, y=100)

# Create a label for the converted currency combobox
converted_currency_label.place(x=30, y=150)

# Create a variable for the amount entry box
amount = StringVar()

# Create an entry box for the amount
amount_entry = Entry(win, textvariable=amount, font=("Arial", 10, "normal"), width=20)

# Create a variable for the currency combobox
currency = StringVar()

# Create a combobox for the currency
currency_combo = ttk.Combobox(win, textvariable=currency, font=("Arial", 10, "normal"), width=18)

# Create a variable for the converted currency combobox
converted_currency = StringVar()

# Create a combobox for the converted currency
converted_currency_combo = ttk.Combobox(win, textvariable=converted_currency, font=("Arial", 10, "normal"), width=18)

# Create a list of currencies
currencies = ["USD", "EUR", "GBP", "INR", "AUD", "CAD", "SGD", "CHF", "MYR", "JPY", "CNY"]

# Set the default value for the currency combobox
currency_combo.set("Select Currency")

# Set the default value for the converted currency combobox
converted_currency_combo.set("Select Converted Currency")

# Add the currencies to the currency combobox
currency_combo['values'] = currencies

# Add the currencies to the converted currency combobox
converted_currency_combo['values'] = currencies

# Create a button to convert currency
convert_button = Button(win, text="Convert", font=("Arial", 10, "bold"), command=exchange)

# Create a button to clear the GUI
clear_button = Button(win, text="Clear", font=("Arial", 10, "bold"), command=clear)

# Create a button to exit the GUI
exit_button = Button(win, text="Exit", font=("Arial", 10, "bold"), command=exit)

# Create an entry box for the amount
amount_entry.place(x=200, y=50)

# Create a combobox for the currency
currency_combo.place(x=200, y=100)

# Create a combobox for the converted currency
converted_currency_combo.place(x=200, y=150)

# Create a button to convert currency
convert_button.place(x=30, y=200)

# Create a button to clear the GUI
clear_button.place(x=130, y=200)

# Create a button to exit the GUI
exit_button.place(x=230, y=200)

# Run the tkinter event loop
win.mainloop()

Run it

run

python currencyexchnageratecalculator.py

A window appears. Enter 100, pick USD → EUR, click Convert, and a popup shows the result.

How it fits together

Read from the top: this is what runs when you execute the file, and which function calls which. It is generated from the code, so it cannot drift from it.

diagram Diagram mermaid

  flowchart TD
  RUN(["python currencyexchnageratecalculator.py"])
  exchange("exchange")
  clear("clear")
  exit("exit")
  RUN --> exchange