Linear Free Energy Relationships (LFERs) quantitatively relate changes in molecular structure to changes in chemical reactivity and represent a well-established and robust approach to deriving mechanistic insight from multiple observations. Historically, LFERs have been carried out using parameters or descriptors obtained from experimental observations for a set of reference processes, such as acid ionization constants (thermodynamic measurements) or relative rate constants (kinetic measurements). These quantitative parameters can, in turn, be related to the outcomes of entirely different reactions. The Hammett relationship is a paradigmatic example in which benzoic acid acidity (an experimentally determined thermodynamic parameter) correlates with the rate for various reactions involving substrates, reagents, or catalysts bearing substituted aromatic rings. A linear correlation between reactivity and the inductive and resonance contributions from metaor para-substituents on aromatic rings (σm and σp Hammett parameters, respectively) reveal the sensitivity of a reaction to these electronic influences. Deviations from linearity may be related to changes in the rate-determining step (e.g., a concave downward curve) or in the mechanism or transition state of the reaction (e.g., a concave upward curve). The ability to relate substituent electronic effects to chemical reactivity is a cornerstone of physical organic chemistry. Several variants of the Hammett parameter, σ, have been derived for experimental reference processes, including Brown's σp + parameters, based on the solvolysis of t-cumyl chlorides, Arnold's σ⍺ parameters, based on spin delocalization of substituted benzyl radicals, Creary's σC parameters, based on methylenecyclopropane rearrangements, and Jiang and Ji's σjj parameters, based on trifluorostyrene cyclodimerizations. Alternative experimental measures, for example electrode polarization effects, have also been related to Hammett parameters. However, as quantum chemical methods have improved, computationally derived parameters, for example obtained from density functional theory (DFT) calculations, have emerged as an alternative for the quantitative description of molecules and their substituents. Given the broad utility of Hammett relationships in correlating reactivity and selectivity with substituent electronic effects, there have been numerous efforts to obtain parameters/descriptors computationally that avoid the need for measurements of equilibrium constants or which can be employed beyond aromatic substituents. 12 Additional Hammett-like equations have also been derived to capture electronic substituent effects using computational concepts like molecular softness and Fukui functions. Computationally derived electronic parameters are increasingly attractive since they can be obtained for structures and substituents without available experimental data and, due to recent advances in computational workflow automation, are readily accessible for large numbers of functional groups. Another advantage of using computed electronic descriptors vs. tabulated parameters is that additivity does not need to be assumed -multiply substituted aromatics can instead be computed directly. Combined steric and electronic effects have been insightful in describing Hammett relationships, however, many studies rely solely on electronic descriptors. Nevertheless, the departure from experimental descriptor acquisition, obtained from macroscopic "top-down" experimental observations to using computational "bottom-up" descriptors presents several challenges for practitioners. For example, the choice of computational protocol(s) and treatment of the conformational ensemble are critical considerations, particularly where descriptor values are obtained as an ensemble average. More fundamentally, since the quantum mechanical wavefunction/density is inherently delocalized across an entire structure and atomic charges are not themselves experimentally observable, myriad theoretical approaches exist to partition the electronic density, which does not by definition belong to any atom, over the different atoms. Our work is focused on establishing the most appropriate computational protocol for obtaining a correct qualitative and quantitative description of substituent electronic effects at the macroscopic level. To the best of our knowledge, no benchmark comparisons of these protocols against a broad dataset of experimental electronic parameters has been previously reported.