It is well-known that there exist frameworks (without continuous flexions) whose physical models can snap between different realizations due to non-destructive elastic deformations of material. We present a method to measure these snapping capability -- shortly called {\it snappability} -- based on the total elastic strain energy density of the framework by using the physical concept of Green-Lagrange strain. It turns out that the value obtained from this intrinsic pseudometric also gives the distance to the closest singular (shaky, infinitesimal flexible) configuration. In addition the presented theoretical results give further connections between shakiness and snapping beside the well-known technique of averaging and deaveraging. We demonstrate our approach on spatial structures (i.a.\ Siamese Dipyramide, Four-Horn) and compare the obtained results with existing literature.