how fast does hair grow?

Hair growth rates can vary depending on several factors, including genetics, age, sex, and ethnicity, but here are some general guidelines:

Average Growth Rate

• On average, hair on the human head grows about 6 inches (15.24 cm) per year. This translates to approximately 0.5 inches (1.27 cm) per month245.

Weekly Growth

• Hair grows at a rate of about 1/8 of an inch (approximately 3.18 mm) per week5.

Monthly Growth in Millimeters

• Thicker hair (greater than 60 μm in diameter) tends to grow faster, at a rate of about 11.4 mm per month, while thinner hair (20–30 μm in diameter) grows at a rate of about 7.6 mm per month1.

Growth Phases

• Hair growth occurs in cycles with three distinct phases: the anagen (growth phase), catagen (transitional phase), and telogen (resting phase). The anagen phase, during which hair grows, can last from three to five years for scalp hair, with about 85%–90% of hairs on the head in this phase at any given time1.

Overall, while individual rates can vary, the average monthly growth of about 0.5 inches is a commonly cited figure.