\documentclass[12pt]{article}
\newbox\tbox
\parskip\baselineskip
\begin{document}\tracingpages=1 \tracingoutput=1 \showboxbreadth=33 \showboxdepth=3
Max page depth is \the\maxdepth, max box depth is \the\boxmaxdepth

Table
\setbox\tbox=\hbox{\begin{tabular}[t]{|l|}
      \hline
       abc\\
       def\\
       ghj\\
       klm\\
       \hline
     \end{tabular}}\copy\tbox\
has dimensions \the\wd\tbox $\times$ \the\ht\tbox $\times$ \the\dp\tbox

Table
\setbox\tbox=\hbox{\vbox{\hsize=\wd\tbox \boxmaxdepth=.5\tabcolsep \box\tbox}}\copy\tbox\
has dimensions \the\wd\tbox $\times$ \the\ht\tbox $\times$ \the\dp\tbox

\end{document}
