On average, human scalp hair grows about half an inch (approximately 1.25 cm) per month, which totals roughly 6 inches (15 cm) per year

. However, this rate can vary significantly depending on factors such as genetics, age, ethnicity, nutrition, hormone levels, and overall scalp health.

Variation in Hair Growth Rates

• Ethnicity: Asian hair tends to grow faster, up to about 0.8 inch (20 mm) per month, while hair of African descent grows slower, around 0.2 inch (5 mm) per month

. Caucasian hair growth averages around 1 cm per month (12 cm per year), though some studies suggest it can be slightly higher, around 1.3 cm per month

• Genetics: Individual genetic makeup plays a major role, with some people experiencing faster or slower growth regardless of ethnicity

• Other factors: Age, diet, hormone balance, stress, and scalp condition also influence growth rates

Hair Growth Cycle

Hair grows in cycles with three main phases:

• Anagen (growth phase): Lasts 2 to 6 years, during which hair actively grows.
• Catagen (transitional phase): Hair growth slows and stops.
• Telogen (resting phase): Lasts about 3 months before hair sheds and a new cycle begins

Summary

• Average hair growth: about 6 inches (15 cm) per year.
• Range: approximately 6 to 12 inches (15 to 30 cm) per year depending on individual and ethnic factors.
• Growth rate varies month to month and person to person.

Thus, while the typical hair growth in a year is about 6 inches, some people may experience faster or slower growth based on their unique biology and lifestyle