In this chapter we offer a set of rules that can be used to assign physical dimensions to tensor fields and a set of rules for how operators on tensor fields may change their physical dimensions. These rules are designed to maintain the physical dimensional coherence between all tensor relations and facilitate assigning physical dimensions to coupling constants in those physical models that must be confronted with experiment. In Appendix A, we give a table with the physical dimensions of all defined quantities in this book, as well as their values in the modern SI system of units, where relevant.