The study presents the enhancement in analysis formulae and its verification for Electromagnetic Band Gap (EBG) structure using the Eigenmode analysis method. Eigenmode analysis of EBG structure is a compact and prolific method for obtaining its performance parameters like surface bandgap (bandwidth) and resonant frequency. The enhancement in mathematical expressions of the gap width, the capacitance, and the bandwidth is carried out using the simple geometrical shapes like square, circle, and hexagon. The verification of the enhanced formulae of the EBG structure is conducted using complex shapes. The theoretical and simulated results agree with each other up to 94% accuracy.