Hydrogels are three-dimensional network structures consisting of crosslinked polymer chains. When immersed in a solvent, hydrogels swell such that they retain the structural integrity due to presence of crosslinks. The elastic properties of hydrogels depend on the density of crosslinks: the higher the crosslink density, the stiffer the gel. They derive elastic properties from the polymer network and swelling properties from the migration of solvent molecules through the network. Due to high swellability and deformability, hydrogels have found applications in various engineering fields, such as drug delivery systems, tissue engineering, wound dressing, and soft actuators. We present here a continuum framework to describe the elastic responses of hydrogels undergoing finite deformations. An expression for free energy density of hydrogels has been utilised. Constitutive equations of hydrogels subjected to swelling are derived in a finite deformation framework. The model is calibrated by fitting the stress-strain curve of Polyrotaxane (PR) hydrogels in uniaxial tension. The results are verified with the available experimental results.