This paper aims to demonstrate the method by which a single experimental setup may be used in order to determine the geometric calibration constants and the adherence to manufacturing tolerances for a large number of particle accelerator electromagnet models, regardless of their size or function within the linear or storage ring accelerator assemblies. Our method is meant to serve as a more flexible alternative to the widely-used rotating search coil magnetometer method, which may be intractable or impossible for harmonic content measurements involving electromagnet apertures which are either oversized or, respectively, undersized relative to the rotating coil assembly. The hereby proposed method is heavily reliant on the usage of a triaxial Gaussmeter Hall probe together with certain signal processing techniques and an application-specific mathematical interpretation of the magnetostatic context within the core of an accelerator electromagnet. As part of this paper, we build upon both fundamental concepts of electromagnetic field theory and recent advancements in order to provide the proofs and mathematical insight on why this method is justified and how it relates to the rotating coil method, which it attempts to substitute for. Our method’s application is showcased on a quadrupole beam-focuser electromagnet model for the linear accelerator (LINAC) part of Variable Energy Gamma (VEGA) system from ELI-NP. We then compare the results of the experimental activity with FEM simulations of the ideally-occurring field inside the electromagnet apertures and conclude our paper by attempting to explain the inconsistencies between the two sets of results.