Human hair grows at a fairly consistent rate of 0.5 millimeter per day or about 0.5 inch per month. Age, genetics and hormones that can affect the rate of hair growth.
A person?s race also affects hair growth. Asian hair grows the fastest at about 6 inches per year, while African hair grows the slowest at approximately 4 inches per year. Caucasian hair is in the middle range at a little more than 5 inches per year. While hair grows slightly faster in the summer, the difference is not noticeable on an actual person.
Cell division causes hair growth; new cells at the root push the hair forward. The normal human scalp contains 100,000 hair strands and loses 100 strands per day. Hair strands last for one to six years and grow at the same rate everywhere on a person?s head.