This paper proposes a new quantitative parameter on identifying the primary factor for appropriate geometry selection of microstrip patch antennas dedicated to low cross-polarization (XP) applications. The significance of point-symmetric (PS) and non-point-symmetric (NPS) geometries has been analyzed on the basis of ‘Field Asymmetry Ratio’ (FAR), a new parameter, defined to quantify the level of electric field asymmetry leading to XP radiation in any regular shaped microstrip patch antennas. Based on this analysis, a conclusive inference has been established on the importance of point-symmetric patch geometry selections to achieve lower XP radiation. The 6-element circular cluster of shorting pins (CCSP) has been adopted as the XP suppression tool for S-band applications to validate the proposition. An XP suppression of approximately 9 dB at the boresight and 5 dB at ±30°around the boresight in H-plane has been achieved for the square-shaped patch geometry. © 2020 Elsevier GmbH