ColumnWidths

is an option for the low-level function GridBox which specifies the widths to use for columns.

Details

	All	wide enough to fit without breaking lines
	Automatic	available width divided automatically among columns
	Scaled[s]	fraction s of the available width
	n	n ems in the current font
	{w₁,w₂,…}	width specification w_i for column i

With ColumnWidths->{w₁,w₂,…,w_n}, the specification w_n is effectively taken to be repeated if there are more than n columns.
With ColumnWidths->Automatic, a particular column will never use more width than its widest element.
An explicit setting for ColumnWidths overrides ColumnsEqual->True.

Set column widths in units of em-widths:

Set column widths as fractions of total width:

Set all columns to the same width:

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