Generating an effective sizing system that both accommodates a target population’s anthropometric characteristics and maintains efficiency is a significant challenge using traditional methods. This study proposed a men’s pants sizing system using a desirability method that enabled simultaneous optimization of a sizing system with respect to accommodation percentage (anthropometric coverage), loss score (penalty for size fitness), and overlap area (sizing system efficiency). The performance of the desirability method was compared with the existing optimization method. To evaluate its performance, the researcher conducted a case study involving different size category numbers (5–25 size number category) and compared it with a representative existing method. The findings from the case study demonstrated that the desirability method outperformed the optimization method, especially when dealing with a larger number of size categories, except in overlapping areas. Across all size categories, the accommodation percentage of the desirability method was 14% higher than that of the existing methods. In addition, as the number of size categories increased, the differences in loss scores between both methods were diminished. The desirability method can be utilized to establish an ideal sizing system that enhances size fitness, broadens anthropometric coverage, and improves sizing system efficiency for sustainable production in the apparel industry.