Accurate evaluation of transmissibility is central to reliable numerical simulation of gas flow in porous media, because of its pressure-dependent properties such as density and viscosity. In commercial reservoir simulators, inter-block transmissibility is calculated using upstream averaging and in the well-containing grid-block, it is evaluated at the grid-block pressure. This procedure does not capture the physics of flow because gas properties change gradually one grid-block to another and significantly within the well-containing grid-block. This study presents a novel integral-based formulation in which pressure-dependent properties are integrated over a pressure range which provides exact values to be used in transmissibility terms, without invoking assumptions or mathematical averaging. The proposed method is fully physics-based, robust, and straightforward to implement within finite-volume reservoir simulators. Owing to its general derivation, the method is applicable to natural gas reservoirs, CO2 injection and storage for CCUS applications which involves multiphase flow, and hydrogen subsurface storage. This methodology helps obtain pressure and production values more precisely by avoiding unjustified mathematical averaging. Comparison of the results obtained from the proposed formulation with the ones obtained from commercial softwares shows significant improvement when grid-blocks are relatively large and absolute permeability is low.