The aim of the study is to evaluate the water equivalency of the newly developed polymer gel dosimeter [2-acrylamido-2-methyl propane sulfonic acid (AMPS)] in terms of its effective atomic number (Zeff) and effective electron density (Neff). Auto-Zeff computer program was used to calculate the Zeff for photon energies ranging from 0.01 to 1000 MeV. 2-Acrylamido-2-methyl propane sulfonic acid polymer gel shows the good water equivalency with less than 1.56 % deviation from water over the energy range of 0.01 to 1000 MeV. Since 2-acrylamido-2-methyl propane sulfonic acid is less toxic and a very good water equivalent medium for photon energies from 0.01 to 1000 MeV it can be employed in clinically. The study also reveals that it is a good alternative gel for poly acrylamide gelatin tetrakis hydroxyl phosphonium chloride (PAGAT) in terms of its less toxicity and water equivalency.