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.
Body hair
Facial hair, as the name suggests, grows primarily on or around one's face. Both men and women experience facial hair growth. Like pubic hair, non-vellus facial hair will begin to grow in around puberty. Moustaches in young men usually begin to grow in at around the age of puberty, although some men may not grow a moustache until they reach late teens or at all. For some cases facial hair development may take longer to mature than in the late teens but a lot of men experience no facial development even at an older age. Facial hair development has often been associated with stress levels.