If a window reaches a certain dimension on MS Windows, it looks unaesthetic if it is centered without respect to the '''taskbar'''. E.g., if the taskbar is at the top, the window should slightly move down, if the taskbar is on the left, it should slightly move to the right and so on. The other examples I found here on the wiki and ::tk::placeWindow (at least up to a certain version) ignore the taskbar. So here is my try: ---- proc center_window {w} { set tw ${w}_temp_ catch {destroy $tw} toplevel $tw wm attributes $tw -alpha 0.0 ; # vermeidet flickern wm state $tw zoomed update idletasks foreach {areaW areaH offsX offsY} [split [winfo geometry $tw] x+] {break} destroy $tw # foreach {winW winH d d} [split [winfo geometry $w] x+] {break}; # turned out to be problematic set winH [winfo reqwidth $w]; set winH [winfo reqheight $w] set x [expr { (($areaW - $winW) / 2) + $offsX }] set y [expr { (($areaH - $winH) / 2) + $offsY }] wm geom $w +$x+$y wm deiconify $w update idletasks } ---- # A simple test wm withdraw . wm geometry . 1200x900 # tk_messageBox -message "[winfo width .]x[winfo height .]\n[winfo reqwidth .]x[winfo reqheight .]" -title debug # update # tk_messageBox -message "[winfo width .]x[winfo height .]\n[winfo reqwidth .]x[winfo reqheight .]" -title debug # tk_messageBox -message "[winfo geometry .]" wm title . "Testtitel" center_window . ---- See: * [Centering a window] ---- !!!!!! %| Category GUI |% !!!!!!