The present study aimed at verifying the water equivalency of the PAGAT gel and metal nano particle (different concentration of gold and silver) PAGAT (MPAGAT) gel in terms of effective atomic number (Zeff). In addition to Zeff, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) have been calculated for MPAGAT. Auto-Zeff computer program was used to calculate the effective atomic number for MPAGAT in the energy region 10 keV to 1 GeV. EABF and EBF were calculated by using geometric progression (GP) fitting formula in the energy region from 0.015 to 15 MeV up to penetration depths of 40 mean free path. Mass attenuation coefficient of MPAGAT gel was obtained by the XCOM program and the results were compared with Monte Carlo simulation. It has been found that Au and Ag doped PAGAT gels show excellent water equivalency than undoped PAGAT gel at dopant concentrations of 0.1, 0.5 and 1 mM. From the results, it was noted that the EABF and EBF were significantly varied with respect to photon energy and chemical composition of given PAGAT gel with different concentration of metal nano particle. Since mass attenuation coefficients were used to obtain Zeff and EABF, the reliability of the mass attenuation coefficient data were cross checked with Monte Carlo simulation, and a good agreement was obtained between XCOM and Monte Carlo simulation.