It is well known that the head and face are smaller in female subjects than in male subjects. However, almost all previous studies have quantified the size difference between female and male subjects as simple numerical values, which might not clarify the difference. The present study evaluated the female-to-male proportions of the head and face so as to clarify the sex-related differences. A total of 1939 female subjects and 1398 male subjects were divided into 3 age groups: young (20-39 y), middle-aged (40-59 y), and elderly (60-79 y). The dimensions were classified into 3 categories: 5 cephalic, 3 frontal facial, and 6 lateral facial. The female-to-male proportions of individual dimensions were compared in the 3 age groups using the following formula: female measurement value x 100/(mean of male measurement value). The female-to-male proportions of the cephalic dimension increased with age, with the female cephalic dimensions overall being about 96% of the male cephalic dimensions. The female-to-male proportions of the frontal facial dimension were constant across the age groups, with the female frontal facial dimensions overall being 95% of the male frontal facial dimensions. The female lateral facial dimension increased markedly from the young to middle-aged group and was constant or decreased slightly from the middle-aged to the elderly group. Overall, the female lateral facial dimensions were approximately 97% of the male lateral facial dimensions. The present study will suggest a new approach to elucidate those sex-related dimensional differences that are characteristic of female and male subjects.