Scaling rules were developed and tested for a continuous twin screw wet granulation process using three scales (11, 16, and 24 mm barrel diameter) of twin screw granulators (TSG). The distributive feed screw configuration used produced high porosity granules (50-60%) with broad bimodal size distributions, especially in the 16 and 24 mm TSGs. Three dimensionless numbers, Froude number (Fr), liquid-to-solid ratio (LSR), and powder feed number (PFN), were identified and their effect on granule size distribution (GSD), porosity and liquid distribution tested. Granule size increased with increasing LSR as expected. However, Fr and PFN had no significant effect on d(10) or d(50) and only a small effect on d(90). In contrast, granulator scale had a strong effect on GSD, with d(90) increasing almost linearly with barrel diameter. This is consistent with breakage of large granules being a dominant mechanism and directly controlled by the geometry of the screw. (c) 2016 American Institute of Chemical Engineers AIChE J, 63: 921-932, 2017