The average rate of human hair growth in a year is 6 inches (about 15 centimeters).
When it comes to different races, the hair growth rate changes slightly.
- Hair growth rate of Asian female is 6 inches per year.
- Hair growth rate of African female is 4 inches (10 cm) per year.
- Hair growth rate of Caucasian female is a little more than 5 inches (13 cm) per year.
The hair growth rate of male didn’t significantly differ from that found for women.
Hair grows quicker in the summer due to dietary changes (eating more fruits and vegetables), as well as shifts in hormones and increased exposure to UV radiation.