We present a fully 3D model to solve Usadel’s equations in arbitrary geometries using COMSOL Multiphysics. Using this model, we predict the magnitude of the proximity effect or inverse proximity effect in micro scale superconducting devices. Calculating a spatially resolved electronic density of states allows us to determine the thermal and electrical transport properties of arbitrary superconductive electronic devices at mK temperatures. The performance of such devices could be significantly impacted by any unexpected proximitization or inverse proximitization. For example, in the 2D bilayer approximation, thin normal metals in contact with superconductors may no longer conduct electronic heat, but this effect is complicated by real device geometries and the particular properties of the normal and superconducting metals. This work goes beyond bilayer approximations and quasi 2D methods to allow for accurate calculation of transport phenomena in proximitized normal metals and in inversely proximitized superconductors.