This method is for determining the apparent bulk density (ABD) of loosely packed spherical catalyst particles with an average particle diameter of 1.6- to 3.2-mm ID. It is also applicable to extruded catalyst particles having a maximum diameter of 3.2 mm, a maximum average length of 9.5 mm, and a maximum individual length of 16 mm. Apparent bulk density is the mass per unit volume of the particulate material.