To convert the theoretical chemical shielding values to chemical shifts, i.e., to be able to compare directly to the experimentally reported chemical shifts, it is necessary to adopt a conversion equation. Theoretically, a simple linear relationship between these scalar characteristics is expected with a slope of -1. Although some studies suggest that this assumption may not be universally applicable, with different elements exhibiting varying slopes, Dib et al. demonstrated that the slope for Al is generally close to -1. For example, Sklenák et al. used a slope of -1 taking the chemical shift of a CHA sample with a high Si/Al ratio, which provided a well-defined experimental Al signal, as a reference. Others proposed to use multiple data points to fit this linear regression dependence achieving slopes mildly modified from -1. However, employing multiple data points to form the conversion equation can be problematic due to uncertainties in modelling the exact experimental structure at the experimental conditions. Therefore, in this study, we assumed a slope of -1 and used Al(acac) 3 , a simple well-defined crystal structure, which is frequently utilized in solid-state Al NMR experiments as a solid reference and has a chemical shift of -4.2 ppm. Lei et. al. performed a 20 ps ab initio molecular dynamics (AIMD) simulation at 300 K with 400 eV cutoff energy, where the chemical shielding values were averaged over 100 snapshots taken uniformly from the trajectory, resulting in an average theoretical chemical shielding of 554.00 ppm. Based on the assumption of a theoretical slope of -1, we derived the following calibration equation: