One column not vertically and horizontally centered

Question

I am trying to center the text in a table both vertically and horizontally. I thought I had managed to do so, but the last column is only centered horizontally. The code I am entering is

\documentclass[11 pt, a4paper, twoside]{report}
\usepackage{array}
\begin{document}

\begin{table} [h]
\centering
\caption{}

\begin{tabular}{ | >{\centering\arraybackslash} m{3cm} | >{\centering\arraybackslash} m{3cm} | >{\centering\arraybackslash} m{4cm} | }
    \hline
    \rowcolor{lightgray} \textbf{Variable} & \textbf{Description} & \textbf{Value} \\ [0.5cm]
\end{tabular}
\end{table}

\end{document}

and it appears

Answer 1

For a solution which still uses \rowcolor and stuff see @AboAmmar's answer. But if you have the freedom of formatting your tables yourself, consider ditching the colours and vertical rules and use booktabs. Also text like in the "Description" column looks better, if it's left aligned. And consider using p columns instead of m.

\documentclass[]{article}

\usepackage{array}
\usepackage{booktabs}

\begin{document}

\begin{table} [h]
\centering
\caption{}
\begin{tabular}{ >{\centering\arraybackslash} p{3cm} p{3cm} >{\centering\arraybackslash} p{4cm} }
  \toprule
    Variable & Description & Value \\
  \midrule
    Variable & Description which really needs the full width& Value \\
    Variable & Description & Value \\
    Variable & Description & Value \\
  \bottomrule
\end{tabular}
\end{table}
\end{document}

And generally values shouldn't be that wide that you need multiple lines to format them. Instead consider using a S-type column provided by siunitx which horizontally aligns the numbers to have the same digits beneath each other (You need to hide the table header from that by enclosing it with {Value}). And variable names shouldn't be that wide, too, so perhaps use the c or the l specifier there. Additionally if each variable name is to be typeset in math-mode, you can use >{\(}c<{\)} to change that column to use math mode. A \hbox can be used to hide something from that effect (or \text provided by amsmath).

\documentclass[preview,border=2mm]{standalone}

\usepackage{array}
\usepackage{booktabs}
\usepackage{siunitx}

\begin{document}

\begin{table} [h]
\centering
\caption{}
\begin{tabular}{ >{\(}c<{\)} p{3cm} S }
  \toprule
  \hbox{Variable} & Description & {Value} \\
  \midrule
  x & Description which really needs the full width& 0.12 \\
  \sigma & Description & 10.51 \\
  \delta & Description & 15.43 \\
  \bottomrule
\end{tabular}
\end{table}
\end{document}

Answer 2

Don't use \\[0.5cm] to increase the first row height. This is the cause of misalignment in the last cell. You can use your own \strut to do this via a $\vcenter{\hbox{\rule{0cm}{.5cm}}}$, for example, or more easily by adding the bigstrut package and using its bigstrut macro.

Also, you can define \newcolumntype{C}[1]{>{\centering\arraybackslash} m{#1}} for brevity and re-usability of your code.

\documentclass{article}
\usepackage{xcolor}
\usepackage{colortbl}
\usepackage{bigstrut}
\begin{document}

\newcolumntype{C}[1]{>{\centering\arraybackslash} m{#1}}
\begin{table}[h]
\centering
\caption{}
\begin{tabular}{ |C{3cm} |C{3cm} | C{4cm} | }
  \hline
  \rowcolor{lightgray} \textbf{Variable} & \textbf{Description} & \textbf{Value}\bigstrut \\ \hline 
  Variable & Description & Value \\ \hline 
  Variable & Description & Value \\ \hline 
  Variable & Description & Value \\ \hline 
\end{tabular}
\end{table}

\end{document}