Application.Width Property (Excel)

Returns or sets a Double value that represents the distance, in points, from the left edge of the application window to its right edge.

expression .Width

expression A variable that represents an Application object.

If the window is minimized, Width is read-only and returns the width of the window icon.

This example expands the active window to the maximum size available (assuming that the window isn’t maximized).

With ActiveWindow 
 .WindowState = xlNormal 
 .Top = 1 
 .Left = 1 
 .Height = Application.UsableHeight 
 .Width = Application.UsableWidth 
End With