How can I put a caption on the following tikz drawing?

Question

documentclass[tikz,border=2mm]{standalone} 

\usetikzlibrary{positioning, calc}

\begin{document}

\begin{centre}

\begin{tikzpicture}


\newcommand{\radiusx}{2}
\newcommand{\radiusy}{.5}
\newcommand{\height}{6}

\coordinate (a) at (-{\radiusx*sqrt(1-(\radiusy/\height)*(\radiusy/\height))},{\radiusy*(\radiusy/\height)});

\coordinate (b) at ({\radiusx*sqrt(1-(\radiusy/\height)*(\radiusy/\height))},{\radiusy*(\radiusy/\height)});

\draw[fill=gray!30] (a)--(0,\height)--(b)--cycle;

\fill[gray!50] circle (\radiusx{} and \radiusy);

\begin{scope}
\clip ([xshift=-2mm]a) rectangle ($(b)+(1mm,-2*\radiusy)$);
\draw circle (\radiusx{} and \radiusy);
\end{scope}

\begin{scope}
\clip ([xshift=-2mm]a) rectangle ($(b)+(1mm,2*\radiusy)$);
\draw[dashed] circle (\radiusx{} and \radiusy);
\end{scope}

\draw[dashed] (0,\height)|-(\radiusx,0) node[right, pos=.25]{$h$} node[above,pos=.75]{$r$};

\draw (0,.15)-|(.15,0);
\end{tikzpicture}
\end{centre}
\end{document}

How do I add a caption that is centered with this tikz drawing because when I do \caption, the entire drawing goes to the left. I also am using this diagram from another thread.