How fast does hair grow?

Each hair grows from a follicle and goes through a cycle with three main phases. The growth phase, called anagen, lasts 2 to 7 years for scalp hair, and it decides how long your hair can grow before it naturally falls out. A short transition phase follows, and then a resting phase of about three months before the hair sheds and a new one starts. At any time, about 85 to 90 percent of scalp hairs are in the growth phase. Genetics, age, nutrition and hormones all affect speed, and hair tends to grow slightly faster in summer.