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.
Hair removal
Hair typically grows all over the human body. Hair can become more visible during and after puberty and men tend to have thicker, more visible body hair than women.
Both men and women have visible hair on the head, eyebrows, eyelashes, armpits, pubic region, arms, and legs; men and some women also have thicker hair on their face, abdomen, back and chest. Hair does not generally grow on the lips, the underside of the hands or feet or on certain areas of the genitalia.