Various dimensionless characterizations of the solid-fluid situation during settling of a spherical particle are surveyed and related to the Archimedes number. The new landmark drag correlation developed recently is rearranged into a quadratic equation of the terminal Reynolds number. Its solution is an explicit equation of the terminal velocity of a settling sphere depending only on the Archimedes number. This new relationship is compared with a few other explicit relations existing in the literature to predict the terminal Reynolds number of spheres. (C) 2019 Published by Elsevier B.V.