Centring a very wide figure or table

The normal means of centring a figure or table object is to include \centering at the top of the float. This doesn’t help if the object is wider than \textwidth — the object starts at the left margin and juts out into the right margin (which is actually doubly unsatisfactory, since as well as looking bad, the float won’t be placed until the next \clearpage or the like.)

You can avoid the problem by rescaling the figure or table to fit, but this is often not satisfactory, for several reasons.

Otherwise, if the object is wider than the printable area of the page, you’ve no choice other than to rotate it. If, however, the object is just wider than the text block, you can make it pretend to be the right size by:

\begin{figure}
  \noindent
  \makebox[\textwidth]{\includegraphics{my-wide-figure}}%
  \caption{This figure juts out into both margins}
\end{figure}
Note the \noindent: the \makebox starts a paragraph, and you really don’t want that indented by \parindent.