We investigate the impact of substitutional magnesium (Mg) doping on the electrical properties of bulk In 0 .5Ga 0 .5N through first principle based density functional theory calculations. Based on binding energy calculations, we explicitly show that In is the most favorable site for substitutional doping of Mg in In 0 5 Ga 0 5 N, as expected. We also calculate the electrical properties like electronic dispersion, binding energy, density of states (DOS), projected DOS, band gap variation and charge carrier's effective masses for intrinsic and Mg doped In 0 5 Ga 0 5 N; via self-consistent and non-self-consistent calculations. We show that Mg doping converts intrinsic In 0 5 Ga 0.5 N into a p-type material, which can potentially be useful for solar cell applications, LEDs and nanocolumn applications.