This study was done to establish clothing sizing system which can provide good fitting of apparel and minimize the loss due to excess inventory. One demensional mesurments(R. Martin) were made with the subjects, who were girls aged 11 to 12 living in Pusan and Kyungnam. Further the above-said mesurements were used to determine optimal clothing sizes using loss function for establishment of clothing sizing system. According to the results, optimal sizes of upper clothing for the late elementary schoolgirls should include 7 sizes, which will include heightbust circumferencesleeve length. And optimal sizes of lower clothing for the late elementary schoolgirls should include 7 sizes, which will include heightbust circumferencehip circumference.