Hybrid organic-inorganic halide perovskites (HaPs) have shown many properties that are advantageous for efficient renewable energy applications. Several of the open questions for these systems can be addressed by first-principles calculations applying density functional theory (DFT). However, in order to achieve reliable insight from such calculations, it is important to understand which of the various microscopic effects in the different DFT-related approximations play an important role in the calculations. Here, we present an investigation on the importance of various theoretical aspects in the DFT calculations of the structural properties for MAPbI₃. We focus on a comparison of calculations varying the DFT functional, the account of van-der-Waals interactions as well as the inclusion of spin-orbit coupling. Our computed unit-cell volumes and bulk moduli are compared to results of experiments, addressing the relative importance of these effects on calculations of structural properties of MAPbI₃. Finally, we also present results on the impact of temperature-induced structural fluctuations on calculating the structural properties of MAPbI₃.