This study presents a numerical simulation of unconfined compression tests (UCTs) on sandstone, utilizing the Discrete Element Method (DEM) in LS-DYNA. The primary objective of this research was to find an optimal mesh configuration to imitate the laboratory testing process by numerical modeling to enhance the reliability of data and reduce the time and cost required for complex experiments. Laboratory-derived rock properties were integrated into the DEM simulation as input parameters. Five numerical models were simulated with varying mesh densities to optimize mesh size. The results were validated by comparing failure mode, stress-strain curves, and uniaxial compressive strength (UCS) with experimental data. A model with a mesh size of 40/30 elements illustrated the closest correlation to the laboratory test, exhibiting a similar stress-strain curve pattern and a minimal UCS difference of 2.62%. Additionally, the failure modes observed in both simulations aligned closely. This similarity between the results of the laboratory experiment and the numerical model proves the efficiency of the numerical model in simulated laboratory tests and offers an opportunity to calibrate the micro-parameters of other constitutive models which can save both the time and money required to determine complex parameters, especially avoiding the risk of critical laboratory experiments.