In this paper, we present the effectiveness of the IRelast package for the elastic constants (ECs) of crystals with different symmetries like Cubic, Hexagonal, Tetragonal, Orthorhombic, Rhombohedral and Monoclinic which are further used to investigate elastic and mechanical properties. The calculated results confirm the usefulness of the software by reproducing consistent experimental results. The reason for this competency is energy approach, where the calculated total ground state energy E(y,εij) is used for the calculations of the ECs. The software is also incorporated into the WIEN2K package. The purpose of the software is to provide a theoretical tool for researchers to calculate ECs of the unknown compounds and calculate ECs for experimentally measured ones for comparison purpose.