This depends on the margins of your document. If you load geometry
, you'll have more sensible margins.
Other than that, you can play with the font size used in the table and the value of \tabcolsep
.
I propose two solutions without geometry
, one with the general look of your code (horizontal and vertical rules), improved with the help of hhline
and cellspace
, which defines minimal vertical padding at the top and bottom of cells in columns with specifiers prefixed with the letter S
(Sc
here, instead of c
). Without geometry we have to reduce the font size to \footnotesize
and \tabcolsep
to 5pt
.
The other solution, with only horizontal rules, uses booktabs
, which defines some vertical padding around rules of varying thickness. The middle rule is slightly trimmed with the (lr)
argument. The font size is \normalsize
, and \tabcolsep
is 3.5pt
.
\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{showframe}
\usepackage{mathtools}
\usepackage{array, caption, hhline, cellspace, booktabs}
\setlength\cellspacetoplimit{4pt}
\setlength\cellspacebottomlimit{4pt}
\renewcommand*\ShowFrameLinethickness{.3pt}
\begin{document}
\begin{table}[!ht]
\centering\footnotesize\setlength\tabcolsep{5pt}
\caption{Table 1}
\begin{tabular}{||*{10}{Sc|}|}
\hline
$ σ$ & $V₀$ & a(1) & b(1) & (b-a)(1) & $ \hat{τ}$(1) & a(2) & b(2) & (b-a)(2) & $ \hat{τ}$(2) \\
\hhline{*{10}{=}}
1 & 1 & 0.4151 & 2.4093 & 1.9942 & 0 & 0.6180 & 1.6180 & 1.0000 & 3.1416 \\
\hhline{||*{10}{-}||}
5 & 2.2361 & 0.2306 & 4.3367 & 4.1061 & 0 & 0.3820 & 2.6180 & 2.2360 & 3.1416 \\
\hhline{||*{10}{-}||}
10 & 3.1623 & 0.1830 & 5.4640 & 5.2810 & 0 & 0.2897 & 3.4520 & 3.1623 & 3.1416 \\
\hline
\end{tabular}
\end{table}
\begin{table}[!hb]
\centering\setlength\tabcolsep{3.5pt}
\caption{Table 1}
\begin{tabular}{@{\,\,}*{10}{c}@{\,\,}}
\toprule
$ σ$ & $V₀$ & a(1) & b(1) & (b-a)(1) & $ \hat{τ}$(1) & a(2) & b(2) & (b-a)(2) & $ \hat{τ}$(2) \\
\cmidrule(l{3pt}r{3pt}){1-10}
1 & 1 & 0.4151 & 2.4093 & 1.9942 & 0 & 0.6180 & 1.6180 & 1.0000 & 3.1416 \\
\addlinespace
5 & 2.2361 & 0.2306 & 4.3367 & 4.1061 & 0 & 0.3820 & 2.6180 & 2.2360 & 3.1416 \\
\addlinespace
10 & 3.1623 & 0.1830 & 5.4640 & 5.2810 & 0 & 0.2897 & 3.4520 & 3.1623 & 3.1416 \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
\begin{center}...\end{center}
in a float. Disregarding this, I see 10 columns in the output