This study introduces a novel mathematical model designed to analyse the antimicrobial susceptibility of microorganisms using the disc diffusion method. The primary objective is to provide a more accurate and efficient interpretation of inhibition zone data, thereby improving the reliability of susceptibility testing. We developed the mathematical model based on a molar concentration of antibiotic and molar zone of inhibition concentration that account for key variables, including the model being validated using experimental data from disc diffusion tests diffusion coefficients, zone of inhibition, and antimicrobial agent potency. That was done on Staphylococcus aureus ATCC 25923 bacterial strains with 22 different antibiotics of beta-lactam group. Our results demonstrate that the proposed model offers significant improvements in predicting the comparative potency and enlisting the priority of antimicrobial agents based on Equivalent molar zone number and Zone of inhibition potency compared to traditional interpretation methods. Specifically, the model achieved a correlation coefficient of 0.9167 with experimental data, indicating high predictive accuracy. Additionally, it can adjust for factors of molar concentration, ZOI, and breakpoint, providing more nuanced insights into antimicrobial efficacy. These findings suggest that the novel mathematical model can be a valuable tool for microbiologists and clinicians, enabling more precise assessments of antimicrobial susceptibility and selecting effective treatment regimens.