In this paper we present the {\tt C++} package {\tt CRunDec} which implements all relevant formulae needed for the running and decoupling for the strong coupling constant and light quark masses. Furthermore, several formulae are implemented which can be used to transform the heavy quark masses among different renormalization schemes. {\tt CRunDec} is the {\tt C++} version on the {\tt Mathematica} package {\tt RunDec} containing several updates and improvements.