For clarity, I need the grid to be wider than the text width so that my figures are large enough to read.
I have tried this:
\begin{figure}
\centering
\begin{tabular}{ccc}
\subcaptionbox{caption\label{1}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{2}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{3}}{\includegraphics[width = 2in]{figure}}\\
\subcaptionbox{caption\label{1}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{2}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{3}}{\includegraphics[width = 2in]{figure}}\\
\subcaptionbox{caption\label{1}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{2}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{3}}{\includegraphics[width = 2in]{figure}}\\
\subcaptionbox{caption\label{1}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{2}}{\includegraphics[width = 2in]{figure}} &
\subcaptionbox{caption\label{3}}{\includegraphics[width = 2in]{figure}}\\
\end{tabular}
\caption{caption}
\label{label}
\end{figure}
But the whole structure is off centre slightly towards the right. How can I centre it?