SignificanceAll tetrameric cation channels share the same pore domain with the characteristic helix–pore-loop–helix architecture. Canonical cation channel function involves ion selectivity by the pore loops and gating by movements of the pore-lining helices. However, much less is known about the physics of the gating process. Here, I took advantage of MthK structures and an entropic polymer stretching physics model to derive the forces and energies involved in channel gating. In MthK, conformational changes in the gating ring alone pull the channel open via unfolded linkers, offering the unique opportunity to use a physical model to calculate the forces, 9.8 pN (piconewton), and energies, 3.6kBT, involved in gating.