when scaling the size of the font in python the size of the button changes

Width and height of the button in letters (if displaying text) or pixels (if displaying an image).

Here’s one way to go, by using size of image to limit size of button when font size changed. Not sure if it is best one.

import tkinter as tk
from PIL import Image, ImageTk

def new_font():
    global setting
    setting = 1 - setting
    font = f"ariel {32 if setting else 16}"
    button.configure(font=font)

setting = 0

root = tk.Tk()

im = Image.new("RGB", (200, 200))
photo = ImageTk.PhotoImage(im)

root.geometry("300x300")
root.resizable(False, False)
button = tk.Button(
    root,
    text="Ihsan",
    bg="Black",
    fg="white",
    activeforeground="white",
    activebackground="grey",
    width=200,
    height=200,
    font=("ariel", "16"),
    image=photo,
    compound='center')

button.place(x=30, y=20)
size = tk.Button(root, text="Size", command=new_font)
size.place(x=30, y=250)

root.mainloop()