The determination of the grade distribution of solid particles is fundamental for the performance analysis of several pieces of equipment promoting the solid-fluid separation. The main objective of this work is to compare the results obtained for two traditional methodologies for determination of the sized grade distribution of powdery solids: the gamma rays attenuation technique (GRAT) and LADEQ test tube technique. The influence of draining of suspension in the two used techniques was also analyzed. The gamma rays attenuation technique can supply the grade distribution of solids through the monitoring of solid concentration in experiments of batch settling of diluted suspensions. The results show that the usage of the peristaltic pump in GRAT and LADEQ methodologies presented a significant difference among the values obtained for the parameters of the particles size model.