Csdrhrt

I have a table with two columns and 12 rows.
I require the table to appear on the left hand side of the page (which I can do), however, the caption is centered on the page.
I would like to place the caption underneath the table, and have it centered underneath the table.
The output is shown below.

documentclass[12pt,english]{article}

usepackage{caption}

begin{document}

 begin{table}[H]

 begin{tabular}{|c|>{centering}p{2cm}|}

 hline 

  Year & Population (millions)tabularnewline

  hline 

   $1900$ & $1650$tabularnewline

   $1910$ & $1750$tabularnewline

   $1920$ & $1860$tabularnewline

   $1930$ & $2070$tabularnewline

   $1940$ & $2300$tabularnewline

   $1950$ & $2560$tabularnewline

   $1960$ & $3040$tabularnewline

   $1970$ & $3710$tabularnewline

   $1980$ & $4450$tabularnewline

   $1990$ & $5280$tabularnewline

   $2000$ & $6070$tabularnewline

   hline 

  end{tabular}

  raggedright{}caption{World Population}label{table1}

  end{table}

 end{document}

Here is a way (since you already want [H] option and have loaded the caption package I suppose it will be ok for you):

documentclass[12pt,english]{article}

usepackage{caption}

usepackage{array}

begin{document}

 % A noindent is possibly needed here as @Mico suggested in his comment

 noindentbegin{minipage}{0.35textwidth}

 centering

 begin{tabular}{|c|>{centering}p{2cm}|}

 hline 

  Year & Population (millions)tabularnewline

  hline 

   $1900$ & $1650$tabularnewline

   $1910$ & $1750$tabularnewline

   $1920$ & $1860$tabularnewline

   $1930$ & $2070$tabularnewline

   $1940$ & $2300$tabularnewline

   $1950$ & $2560$tabularnewline

   $1960$ & $3040$tabularnewline

   $1970$ & $3710$tabularnewline

   $1980$ & $4450$tabularnewline

   $1990$ & $5280$tabularnewline

   $2000$ & $6070$tabularnewline

   hline 

  end{tabular}

  captionof{table}{World Population}label{table1}

  end{minipage}

 end{document}

Since the tabular material must be typeset flush-left (aka ragged-right), I think the caption would look better if it, too, where set flush-left. (However, see below for a different solution.) One can achieve this formatting objective by loading the caption package with the options singlelinecheck=false and justification=raggedright.

documentclass[12pt,english]{article}

usepackage{array,caption}

captionsetup{singlelinecheck=false,justification=raggedright}

begin{document}

begin{table}[ht!]

 begin{tabular}{|c|>{centeringarraybackslash}p{2cm}|}

 hline 

   Year & Population (millions)\ hline 

   $1900$ & $1650$\

   $1910$ & $1750$\

   $1920$ & $1860$\

   $1930$ & $2070$\

   $1940$ & $2300$\

   $1950$ & $2560$\

   $1960$ & $3040$\

   $1970$ & $3710$\

   $1980$ & $4450$\

   $1990$ & $5280$\

   $2000$ & $6070$\ 

 hline 

 end{tabular}

caption{World Population}label{table1}

end{table}

end{document}

Alternatively, if the caption must be centered below the tabular material and the tabular material must be typeset flush-left, I suggest you (a) run captionsetup{justification=centering}, (b) load the threeparttable package, and (c) encase both the tabular environment and the caption statement in a threeparttable environment. This setup allows LaTeX to measure the width of the tabular material and to center the caption below the tabular; if needed, LaTeX will automatically insert line breaks in the caption. This behavior is shown in the following screenshot.

documentclass[12pt,english]{article}

usepackage{array,caption,threeparttable}

captionsetup{justification=centering}

begin{document}

begin{table}[ht!]

begin{threeparttable}

 begin{tabular}{|c|>{centeringarraybackslash}p{2cm}|}

 hline 

   Year & Population (millions)\ hline 

   $1900$ & $1650$\

   $1910$ & $1750$\

   $1920$ & $1860$\

   $1930$ & $2070$\

   $1940$ & $2300$\

   $1950$ & $2560$\

   $1960$ & $3040$\

   $1970$ & $3710$\

   $1980$ & $4450$\

   $1990$ & $5280$\

   $2000$ & $6070$\ 

 hline 

 end{tabular}

caption{World Population}label{table1}

end{threeparttable}

end{table}

end{document}