Regular haircut
Human scalp hair grows on average about one eighth inch per week or one half inch per month. Most clipper guards are numbered in eighths of an inch. The number of the guard denotes the number of weeks of hair growth left on the scalp when a clipper with a certain numbered guard is guided over the head with the guard in contact with the scalp. A #1 guard leaves 1/8 inch (3 mm), one week's growth of hair, on the scalp; a #2 guard leaves 2/8" (6.3 mm), two weeks' hair growth, on the scalp; a #3 guard leaves 3/8" (9 mm), three weeks' hair growth on the scalp; and so on.
Long hair
In most current cultures, it is more typical for women to wear long hair than for men to do so. An American study shows significant correlation between hair length and age, which indicates that younger women tend to have longer hair than older women. A significant correlation was also found between women's hair length and hair quality. Moreover, hair quality was correlated with the women's perceived physical health. Consistent with principles of evolutionary psychology, these results indicate that hair length and quality can act as a cue to a woman's youth and health, signifying reproductive potential. The correlation between the woman's hair length and marital status, or number of children, was however not more than to be expected from the correlation between hair length and age.