Let $(G_t)_{t\in T}$ be a centred Gaussian process with canonical semimetric $d_G$. Assume $(T,d_G)$ is [totally bounded](/page/Totally%20Bounded) and that the process is separable with respect to $d_G$. There exist universal constants $c,C>0$ such that \begin{align*} c\,\gamma_2(T,d_G) \le \mathbb E\left[\sup_{s,t\in T}|G_t-G_s|\right] \le C\,\gamma_2(T,d_G). \end{align*}