The three stages of hair growth are the anagen, catagen, and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form. The growth rate of hair varies from individual to individual depending on their gender, age, genetic predisposition and countless environmental factors. On average, the growth rate for human hair is about 1.25 centimetres or 0.5 inches per month, or about 15 centimetres or 6 inches per year.