Hair grows about 1/2 inch per month. If the rest of the scalp hair is long, it may take months or years before a shaved area grows sufficiently to match the rest of the hair.
After shaving, the hair growing back may appear to be thicker and coarser, because the shaving process removes the natural thin ends of the hair. Eventually, the shaved hairs are shed and replaced with normal hair. Scalp hairs may only be shed every two to six years.
Scalp hairs grow continuously most of the time. The active growth phase, called anagen, can last for up to six years. In the telogen phase, the hairs stop growing and become dormant for approximately 100 days and are then shed. Most people shed 25 to 100 scalp hairs per day.