The study evaluated the engineering and physical characteristics of eight millet species to generate baseline data for post-harvest processing and storage. Grain samples analysed included finger millet (KMR 301), sorghum (CSV 15), pearl millet (MPMH 21), proso millet (TNAU 202), foxtail millet (SiA3156), little millet (CLmv1), barnyard millet (DHBM 93-2) and browntop millet (HBr 2). The objective was to quantify and compare dimensional (length, width, thickness), geometric (mean diameters, sphericity, projected area, grain volume) and physical (thousand-grain weight, bulk density, true density, porosity) properties of several millet cultivars to inform processing, breeding and policy decisions. Significant interspecific variation was observed across all parameters. Sorghum exhibited the largest grains, while finger millet had the smallest. Bulk density ranged from 0.585–0.810 g/cm³ and true density showed comparatively minor variation, spanning 1.008–1.225 g/cm³. Porosity values ranged between 21.71 and 41.98 %, reflecting differences in grain packing behaviour with direct implications for storage system design. Thousand grain weights varied considerably, from 2.16–23.17 g, underscoring the morphological diversity across species. Statistical analysis confirmed that differences among the eight millet species were significant at p < 0.05. These findings provide reliable engineering data essential for designing species-specific post-harvest processing equipment, handling systems and storage infrastructure, thereby supporting more efficient and optimised millet value chain operations across diverse agro-processing environments.