\begin{tabular}{ | c | c | }
  \hline numer & błąd \\
  \hline 11,1 &  11\\
  \hline 299,05  &  10,1\\
  \hline 3000,5 &  9,3\\ 
  \hline
 \end{tabular}

In my country using , not . as separator. I cant use ‘S’ in tabular header. How centering to comma in tabular enviroments?

I need table with centering by the comma in numbers. I can use r@{\,} but header is not centered.

>Solution :

The siunitx has an option to use , as decimal marker (if you compile with lualatex or xelatex, you don’t need this \fontencoding{T1}\selectfont hack…):

\documentclass{article}

\usepackage[output-decimal-marker={,}]{siunitx}

\begin{document}


 \begin{tabular}{ | S[table-format=4.2] | S[table-format=2.1] | }
  \hline {numer} & {\fontencoding{T1}\selectfont błąd}\\
  \hline 11,1 &  11\\
  \hline 299,05  &  10,1\\
  \hline 3000,5 &  9,3\\ 
  \hline
 \end{tabular}


\end{document}