Purpose <p>The purpose of this study was to investigate how powder fill weight, particle size, and particle size distribution influence force transmission and compaction behavior of powders during compaction within narrow die cavities.</p> Methods <p>Discrete element method simulations were used to model confined powder compaction. Monodisperse and polydisperse systems were analyzed by varying particle size, size distribution breadth, and fill weight. Compaction force–displacement behavior was examined together with particle-level normal, tangential, and cohesive forces, including their axial and radial spatial distributions.</p> Results <p>Particle size had a stronger influence on force heterogeneity than fill weight within the range examined, with larger particles generating higher and more heterogeneous contact forces. Force distributions were positively skewed, indicating load localization within force chains. Normal and tangential forces were highest near the die wall, reflecting strong confinement effects. While individual particle forces followed similar size-dependent trends across different size distributions, narrow distributions required higher compaction forces due to localized load-bearing structures, whereas wider distributions promoted more uniform force sharing and lower resistance to compaction.</p> Conclusions <p>The results demonstrated that macroscopic compaction behavior was governed by the organization of force networks rather than particle-scale force magnitudes alone, highlighting the critical roles of particle size, polydispersity, and confinement effects in powder compaction.</p> Graphical abstract <p></p>