A lifetime of hair adds up to about 26 feet, according to medical evidence. But no one's hair ever grows to that length. That's because each of the 100,000 hair follicles on your head produces one hair shaft, but only for one to six years, usually to a maximum length of 30 to 36 inches. Then the hair "molts," or drops out and is replaced by another.
Follicles grow hair in cycles. After a period of activity, they shrink and rest for three to four months before producing more growth, except in spots where you may be going bald.
But don't think you're going bald because you find lots of loose hairs in your sink and on your comb. The average person molts 30 to 100 hairs a day.