Density-functional theory (DFT) is one of the most reliable simulation methodologies used in materials science. Experimental and computational scientists alike use it to interpret their results and to fit larger scale models. While DFT presents an in-principle exact theory, various approximations are required to perform practical simulations. These approximations can be classified as: (i) controlled approximations, whose errors can be made arbitrarily small at the expense of increased computational cost, and (ii) uncontrolled approximations, whose errors are unknown exactly. To this day, a systematic evaluation of the uncertainties related to either kind of approximation is still lacking and it is the scope of this work. We computed quantities like formation energies, lattice constants and elastic properties for single elements in several phases, using various DFT codes. We then investigated correlations in the precision of the different properties obtained as a function of various convergence parameters (basis set and k-points).