Hydrogels are tridimensional elastic hydrophilic cross-linked polymers with the ability to absorb water in a process called swelling. The Flory-Huggins (FH) theory can be applied to model hydrogel swelling with appropriate adjustments. In the literature the FH model parameter is directly estimated from experimental data on swelling. The target of this paper is to evaluate the effect of using parameters estimated from liquid-liquid equilibria of the linear polymer directly in the swelling modeling of the respective cross-linked polymer as these data can be easily found in literature. Three methods that use different equations for the FH parameter and two methods for the mechanical contribution are evaluated. These models were applied to the polymer poly(N-isopropylacrylamide), PNIPA, and compared in three swelling intervals: the volume contraction region; the transition temperature; and the region of volume expansion. The most relevant and important behaviors of each region are shown, analyzed and discussed. (C) 2016 Elsevier B.V. All rights reserved.