Microstrip patch antennas are well suited for low volume profile, light weight and easy integration. In this paper numerical analysis of stacked three layer Rectangular Microstrip patch antenna with parasitic elements is given. It is found that the antenna exhibits dual resonance. The %Bandwidth is directly depends on height of middle substrate h2 and height of upper substrate h3 and increases with increase in value of h2 and h3. The theoretical value of %bandwidth is found tobe 41.498 % and the simulated bandwidth is found to be 50%. The theoretical results are compared with the simulated results obtained from a soft designer.