We present two applications of the (rather formal) Hawking quasilocal mass construct to cosmology. We first apply it to simulations of large scale structures, which are Newtonian even though the size of the box used exceeds the Hubble radius. The Hawking mass splits into a “Newtonian” part due to local perturbations and a “relativistic” part due to the cosmological background. The Newtonian part quickly dominates over the relativistic one during evolution, supporting the validity of Newtonian simulations. The same splitting is applied to the turnaround radius of a large object in the accelerated era, introducing a small correction and a clarification of the “mass” concept used in previous literature.