For the sake of variety, a LuaLaTeX-based solution.
The default precision displayed by \myPerCent is 3 significant digits. This can be overridden by specifying an optional argument, enclosed in square brackets. With this approach, the two mandatory arguments of \myPerCent don't have to be numbers. All that's required is that they evaluate to numbers using standard math syntax rules.
% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{luacode} % for '\luaexec' macro
\newcommand{\myPerCent}[3][3]{\luaexec{%
tex.sprint( 100 * string.format("\%.#1f",(#2)/(#3)) )
}\,\%}
\begin{document}
\myPerCent{2441}{8667}, \myPerCent[5]{2441}{8667}.
\myPerCent{10/2}{2*3}, \myPerCent[5]{10/2}{2*3}.
\end{document}