The electronic devices such as cell phones, laptops etc. are a necessary part of our daily life that requires portable power sources. Hydrogen being the most abundant element on the Earth, is an excellent energy carrier with high energy capacity that enable to use hydrogen storage methods in portable power sources. In addition, hydrogen storage could he essential to store the energy obtained from the renewable energy sources. The solid state hydrogen storage is an encouraging method for hydrogen storage applications. In this study, Mg3BHx (x=1,4,7) compounds have been studied using Density Functional Theory (DFT) with the Vienna Ab-initio Simulation Package (VASP). The elastic constants have been obtained for the optimized structures. In addition, the band structures have been determined with the corresponding density of states. The gravimetric storage capacities have been determined for these compounds. Mg3BIL compounds with mechanical stability could be promising compounds for hydrogen storage applications.