The effects of particle size on erosion magnitude and erosion profiles are investigated experimentally in a submerged slurry jet impingement facility. The slurries were diluted to avoid concentration effects on the flow field and the resulting erosion. The experiments are performed with particle sizes of 25, 75, 150, 300, and 600 μm. Experimental results demonstrate different erosion severity and pattern for the various particle sizes. It is critical to have a reliable and accurate tool to predict erosion for different particle sizes. Previously, a comprehensive CFD-based procedure to predict erosion for various particle sizes was proposed by investigators at the Erosion/Corrosion Research Center (E/CRC). A feature of this procedure is that it can account for particle size in more detail than previous methods. In this study, the computational procedure is applied to conditions of the present experimental data. Particle impact parameters are extracted to explain the effect of particle size on the resulting erosion. The predicted results are compared with data which demonstrate possible shortcomings of the available CFD based techniques for predicting solid particle erosion. The results indicate that with proper use of grid spacing near the wall, the CFD-based erosion calculation method with existing erosion models can predict the trend of the experimental data, though improvements are still needed to the models to accurately account for particle size effects.