In this study, the sizing systems of 40 unisex sweatshirt brands were analyzed to collect the size information needed to produce unisex clothing. Each size specification was compared with the body size distribution and percentiles of men and women aged 18 to 29. Depending on the brand, unisex sweatshirt sizes ranged from 1 to 8. Despite being unisex apparel, three brands offered only one or two sizes. Out of the brands surveyed, 50% were found to offer four or five sizes. Out of the 40 brands, 25 used letters such as “S,” “M,” and “L” to indicate the size designation. More than 92.5% of the brands included M and L, and the sizing system tended to focus on larger sizes such as XL and 2XL rather than smaller sizes such as XS and S. The size specifications of shoulder width, chest circumference, sleeve length, and total length were compared with the body size distribution and percentiles of men and women aged 18 to 29. The distribution of each size specification mostly appeared in a section larger than the men’s body size. The size specifications of unisex sweatshirts were set close to or larger than men’s sizes and hardly represented women’s sizes. To increase consumer satisfaction with unisex clothing, establishing a size standard that could accurately reflect the body size distribution of men and women was found to be imperative. Such a size standard could also help each brand specify or diversify its target and differentiate itself with other brands.