In this work, we have introduced a variation of the theoretical mean-field model from Denton and Tang for describing swelling of ionic microgels, which improves and extends its application in a wide range of the parametric space. Denton-Tang model combines Poisson-Boltzmann theory for describing electrostatics with Flory-Rehner theory for the polymer properties in order to provide expressions of the microgel osmotic pressure, which is used to determine the microgel equilibrium size. We have incorporated the finite extensibility of the polymer chains in the model by replacing the expression of elastic energy contribution of Gaussian chains by the one from the Langevin model. The later allows to describe the polymer chains with finite extensibility by properly accounting for the effect of the stretching forces in the estimation of the chain end-to-end distance.