# Scale figure to a percentage of \textwidth

I would like to change my figure's width to a precentage of my \textwidth:

\textwidth /2 would scale to 50% of the \textwidth.

What is the proper syntax (if any) to do this ?

 \documentclass{article}

In some cases \linewidth instead of \textwidth may be the better option. For example will it be the same as \textwidth in a single column document, but the same as \columnwidth in a two column document. \linewidth may also change in list environments, becoming smaller in nested lists.