Let \(\mathfrak {F}\) be a free Leibniz algebra generated by a set \(\{x_{1},\ldots ,x_{n}\}\) over a field K of characteristic 0. In this study, we prove that for a homogeneous element u, an arbitrary endomorphism \(\varphi \) of \(\mathfrak {F}\) is an automorphism if and only if u belongs to \(\varphi ( \mathfrak {F})^m\) . As a result, we obtain an algorithm for determining the rank of a homogeneous element and a particular automorphic image of this element that realizes the rank.