As pointed in the comment, you can use the tabularx-package in your preamble.
Tabularx introduces a new column type identifier: X (that is a capital X). The X-column works pretty much the same way, an ordinary p{width}-column does. The difference is: in a p-column, you have to define the width of the column. For the tabularx you have to define the total width of your table. The X-columns are than used to make the columns that big, that the total width of the table reaches the desired value.
Here is an example:
\documentclass[12pt]{article}
\usepackage{tabularx}
\usepackage{booktabs}
\begin{document}
\begin{tabularx}{4cm}{rX}
\toprule
left 1 & Lorem ipsum amet dolores ingrum\\
another line & foo bar baz brave check hat dot ddot\\
\bottomrule
\end{tabularx}
%% Same table somewhat wider
\begin{tabularx}{6cm}{rX}
\toprule
left 1 & Lorem ipsum amet dolores ingrum\\
another line & foo bar baz brave check hat dot ddot\\
\bottomrule
\end{tabularx}
%% And even wider
\begin{tabularx}{8cm}{rX}
\toprule
left 1 & Lorem ipsum amet dolores ingrum\\
another line & foo bar baz brave check hat dot ddot\\
\bottomrule
\end{tabularx}
\end{document}
And its result:

0.9\textwidthis a rather obvious generalization of1.\textwidth. However, I may be wrong! I'll re-open the posting. – Mico Jan 02 '17 at 10:25tabular,tabular*,tabularx, etc) to\textwidth-- to the width of the page block. These methods can be adapted in obvious ways if the intended width is, e.g.,0.9\textwidthor\columnwidth. – Mico Jan 02 '17 at 10:27