Pie charts with LaTeX TikZ

Define a new command to insert a pie slice:

\newcommand{\slice}[4]{
\pgfmathparse{0.5*#1+0.5*#2}
\let\midangle\pgfmathresult

% slice
\draw[thick,fill=black!10] (0,0) -- (#1:1) arc (#1:#2:1) -- cycle;

% outer label
\node[label=\midangle:#4] at (\midangle:1) {};

% inner label
\pgfmathparse{min((#2-#1-10)/110*(-0.3),0)}
\let\temp\pgfmathresult
\pgfmathparse{max(\temp,-0.5) + 0.8}
\let\innerpos\pgfmathresult
\node at (\midangle:\innerpos) {#3};
}


Then define the slices in the order you want to have them and with the percentages and labels. You can start at a different point in the circle by setting the counter ‘d’ to a different value before the loop, e.g. \setcounter{d}{25}.

\begin{tikzpicture}[scale=3]
\newcounter{c}
\newcounter{d}
\foreach \p/\t in {66/, 17/Equative, 10/Difference, 7/}
{
\setcounter{c}{\value{d}}