In order to understand swelling predictions from the different models, we primarily focus on the salt-free limit, where the microgel swelling is most pronounced. Firstly, we consider the swelling of an instructive case and analyze how the equilibrium size depends on the different osmotic pressure contributions. In Fig. , we observe the electrostatic pressure contribution π e and the gel contributions π g for Gaussian and Langevin model versus trial swelling ratio α trial = a trial /a 0 . As observed, π e is positive and decreases for increasing α trial , and increases with growing microgel bear charge at constant swelling α trial . Namely, it mainly contributes to a microgel expansion. This contribution is counteracted by π g , which is smaller that zero for swelling larger that the equilibrium size for neutral case. Recall that the equilibrium microgel swelling is given at the swelling ratio such that π e + π g = 0.