I tested a MWE given in question Standalone producing cropped / truncated formulae. Following the documentation (page 9) I used the class option border={left right bottom top} with left=right=top=0pt and bottom=20pt (20pt only to show the effect here).
With the version 2012/09/15 v1.1b of standalone and the following MWE I get no 20 pt margin at the bottom of my picture. What is the problem?
MWE:
\documentclass[%
% border=1pt
border={0pt 0pt 20pt 0pt} %left right bottom top
]{standalone}% http://ctan.org/pkg/standalone
\begin{document}
$2^5 = x_5 \times y^8$
\end{document}
left right bottom topjust proceeds left-right-down-up, so it doesn't really cover all four sides, whereasleft bottom right top"draws" a rectangle counterclockwise around the boundary. please do notify the author. – barbara beeton Jul 13 '13 at 14:47