Abstract: We describe a method that uses perturbative unitarity constraints to find the characteristic energy scales in theories of thermal Dark Matter. We apply this method to three Dark Matter portals: the NMSSM Higgs sector, a Z' model with a dark Higgs, and a squark simplified model, and derive the projected constraints from ton-scale Direct Detection experiments. We briefly describe projected constraints from a 100TeV collider. We also investigate the physical meaning of unitarity bounds on Dark Matter models and how to set more refined bounds on Dark Matter portals