The paper presents a 3D analysis (3DA) to evaluate the particle shape and size of silica and calcareous sands. The particles of calcareous sand are found to be less spherical than those of silica and crushed calcareous sands. Furthermore, the results indicate that the average sphericity (SPH) holds an inverse relationship to the particle size. However, in each sample the larger particles have higher SPHs than the smaller particles. In addition, the 3DA yields smaller particles than the sieve analysis (SA). Owing to a variety of particle shapes, causing particle interlocking, especially for calcareous sand, the particles cannot pass through the sieves by their shortest dimension. This paper discusses the effects of particle characteristics on the shear strength properties. Although the calcareous sand shows higher peak and residual shear strength properties, it tends to reach a lower shear strength at a small shear strain and a lower dilation than the silica sand. Moreover, the findings prove that the residual shear strength increases with the mean particle size. The sample with smaller particles shows less dilation under low vertical stress, while high vertical stress yields less compression. The relationship between the particle shape and shear strength properties is discussed based on the 3DA results.