In the pharmaceutical lubricant mixing process, lubricity of granules after mixing was evaluated by measuring the contact angle with water and tablet hardness. The granules were prepared using three different types of popular tumble mixers; V-blender (effective volumetric capacity; 70 L), Container blender (36 L) and Bin blender (20 L) with different powder loading rates (10-88%), blender rotation speeds (18-37 rpm) and mixing times (5-120 min) for model placebo formulation. Contact angle measurement and tablet hardness are useful as alternative characteristics for evaluation of granule lubricity. Based on the experimental data, mixing performance index (MN), which is an empirical equation including blender type, powder loading ratio, mixing rotation speed and batch size as functional parameters, was developed. Mixing ability (MA) was defined by the combination of MPI and mixing time. Calculated MA exhibited good correlation with tablet hardness (correlation coefficient is 0.89) in all datasets. MA was verified by nine different drug product data with different manufacturing scales, to enable the MA model to support the formulation researcher to set mixing process parameters when the batch size or blender type changes. (C) 2015 Elsevier B.V. All rights reserved.