Peak-to-valley surface microroughness measurement data acquired from a white light interferometer are compared with data from the actual depth of subsurface damage (SSD) acquired destructively, in single crystalline optical materials (Si, CaF, MgF2, LiNbO3, Al2O3) after deterministic microgrinding (DMG). The results demonstrate that SSD is always less than 1.4 times the peak-to-valley surface microroughness for these crystals regardless of crystallographic orientation. These results enable a maximum depth of SSD to be predicted non-invasively for these single crystal materials. The Center for Optics Manufacturing also has an extensive database comparing surface microroughness to SSD in optical glasses. This data will be presented, demonstrating the upper bound for SSD depth in optical glasses based on the surface microroughness. Interferometer settings and destructive techniques for physically determining SSD will be presented.