How to Set and Manage Window Size in Python Tkinter

Need a 640 by 360 pixel window? Call root.geometry("640x360") on your main window. That string sets the tkinter window size (width first, in pixels); an optional +x+y sets where it opens:

root = tk.Tk()
root.geometry("640x360+120+80")   # width x height + x + y

In this tutorial, I’ll size one small Expense Tracker window on Python 3.12.5 with Tk 8.6: reading, limiting, locking, centering and full screen.

Set the Tkinter window size and position with geometry()

Here’s the Expense Tracker main window. A label shows the size Tk actually gave it:

import tkinter as tk

root = tk.Tk()
root.title("Expense Tracker")
root.geometry("640x360+120+80")    # width x height + x + y

info = tk.Label(root, font=("Segoe UI", 14))
info.pack(expand=True)

def show_size():
    root.update()                  # let Tk apply the geometry first
    info.config(text=f"Size: {root.winfo_width()} x {root.winfo_height()}"
                     f"\ngeometry(): {root.geometry()}")

root.after(100, show_size)
root.mainloop()

The string format is "WIDTHxHEIGHT+X+Y" with a lowercase x and no spaces.

To size the widgets inside it, use a layout manager like the Tkinter pack geometry manager.

How do I get the current Tkinter window size?

Same window, read back. Call root.update() first, or Tk hasn’t drawn it yet:

import tkinter as tk

root = tk.Tk()
root.geometry("640x360")
print("Before update():", root.geometry(), root.winfo_width())

root.update()
print("After update(): ", root.geometry(), root.winfo_width())
print("Width x height: ", root.winfo_width(), "x", root.winfo_height())
root.destroy()

Output:

Before update(): 1x1+0+0 1
After update():  640x360+104+104 640
Width x height:  640 x 360

Before update(), geometry() said 1x1 and the width was 1. Afterward, both report the real 640 x 360 size.

winfo_width() and winfo_height() return integers. The same winfo_* family also gives you the mouse position in Tkinter.

Note: on a laptop with 125% display scaling, Python reports scaled (logical) pixels unless the app is DPI aware, so your numbers may not match a screenshot pixel for pixel.

Limit resizing with minsize() and maxsize()

Users drag window edges, so I set a floor and a ceiling. Same Expense Tracker, plus a button asking for 300 x 200:

import tkinter as tk

root = tk.Tk()
root.title("Expense Tracker")
root.geometry("640x360")
root.minsize(480, 300)             # smallest size allowed
root.maxsize(1000, 700)            # largest size allowed

info = tk.Label(root, font=("Segoe UI", 14))
info.pack(expand=True)

def show_size():
    root.update()
    info.config(text=f"Size: {root.winfo_width()} x {root.winfo_height()}")

def shrink():
    root.geometry("300x200")       # below minsize on purpose
    show_size()

tk.Button(root, text="Shrink to 300 x 200", command=shrink).pack(pady=12)
root.after(100, show_size)
root.mainloop()

minsize() doesn’t just stop mouse dragging; it also clamps geometry() calls from code. That’s why the window ended at 480 x 300, not 300 x 200.

Inside a resizable window, use sticky and weights so widgets stretch with it, as in this Tkinter Frame grid tutorial.

Make a fixed-size Tkinter window with resizable()

For a dialog-style window that should never change size, turn resizing off in both directions:

import tkinter as tk

root = tk.Tk()
root.title("Expense Tracker")
root.geometry("640x360")
root.resizable(False, False)       # (width, height)

tk.Label(root, text="Fixed-size window: 640 x 360",
         font=("Segoe UI", 14)).pack(expand=True)
root.mainloop()

The two arguments are width and height, so resizable(True, False) allows horizontal resizing only. You can also restyle the frame with these Tkinter title bar color options.

Center a Tkinter window on the screen

Same Expense Tracker size. Subtract the window size from the screen size, halve it, then pass the offsets to geometry():

import tkinter as tk

root = tk.Tk()
root.title("Expense Tracker")
w, h = 640, 360
x = (root.winfo_screenwidth() - w) // 2
y = (root.winfo_screenheight() - h) // 2
root.geometry(f"{w}x{h}+{x}+{y}")
root.update()

print("Screen:", root.winfo_screenwidth(), "x", root.winfo_screenheight())
print("Placed at:", x, y)
print("geometry():", root.geometry())
root.destroy()

Output:

Screen: 1536 x 864
Placed at: 448 252
geometry(): 640x360+448+252

Integer division (//) keeps the offsets whole numbers, which geometry() requires.

Tk also has a built-in helper, but it centers the window’s requested size, not the size you set:

import tkinter as tk

root = tk.Tk()
root.geometry("640x360")
root.eval("tk::PlaceWindow . center")
root.update()
print("tk::PlaceWindow:", root.geometry())
root.destroy()

Output:

tk::PlaceWindow: 640x360+668+332

That landed off-center, so I stick with the math. Popups work the same way; see Tkinter multiple windows.

Open a Tkinter window maximized or full screen

On Windows, state("zoomed") maximizes the window and keeps the taskbar. attributes("-fullscreen", True) hides the title bar and covers the whole screen:

import tkinter as tk

root = tk.Tk()
root.geometry("640x360")

root.state("zoomed")               # maximized, taskbar visible
root.update()
print("state():", root.state())

root.state("normal")
root.attributes("-fullscreen", True)   # no title bar
root.update()
print("fullscreen:", root.attributes("-fullscreen"))
root.bind("<Escape>", lambda e: root.attributes("-fullscreen", False))
root.destroy()

Output:

state(): zoomed
fullscreen: 1

Bind Escape to leave full screen, since there’s no close button. On Linux (X11), use attributes("-zoomed", True) instead.

Common Tkinter window size errors and how to fix them

Two errors from building the Expense Tracker:

import tkinter as tk

root = tk.Tk()
for spec in ("640*360", "640x360"):
    try:
        root.geometry(spec)
        print(spec, "-> OK")
    except tk.TclError as err:
        print(spec, "-> TclError:", err)

root.maxsize(1000, 700)
try:
    root.attributes("-fullscreen", True)
except tk.TclError as err:
    print("fullscreen -> TclError:", err)
root.destroy()

Output:

640*360 -> TclError: bad geometry specifier "640*360"
640x360 -> OK
fullscreen -> TclError: can't set fullscreen attribute for ".": max width/height is too small

The first is a typo: geometry() needs a lowercase x. The second surprised me: a maxsize() smaller than the screen blocks full screen, so remove the limit first.

If you’re building a full app around this window, these come next:

• Tkinter Label in Python
• Python Tkinter Button
• Python GUI programming with Tkinter
• Turn a Tkinter script into an .exe

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