A window's size (width and height) is given in pels, in the range 0 through 65535. A window can have 0 width and height; however, a window with 0 width or height is not drawn on the screen, even though it has the WS_VISIBLE style.

An application can create very large windows; however, it should check the size of the screen before enlarging a window size. One way to choose an appropriate size is to use the WinGetMaxPosition function to retrieve the size of the maximized window. A window that is larger than its maximized size will be larger than the screen also.

An application can retrieve the current size of the window by using the WinQueryWindowRect function.