In this study, iron-based amorphous powders with two different sizes, which are the average sizes of 18.92 μm and 74.69 μm, were mixed to increase the powder packing fraction and resulting soft magnetic properties. By varying the mixing ratio, the powder packing fraction was experimentally measured and also estimated by the Desmond model and the computational simulation on the basis of the discrete element method (DEM). As a result, the DEM simulation exhibited higher validity compared to the Desmond model possibly because it accounts for the interaction between the powders, such as repulsion and aggregation, which are not considered in the Desmond equation. Finally, the maximum powder packing fraction of 73.86 % was achieved when the powders were mixed at the ratio of 5:3 (~25 μm: 45~63 μm). This ratio produced an increase of 32.5 % for coercivity and 17.8 % for saturated magnetization compared to the case of 100 % large powders with a 74.69 μm average diameter.