Hair typically grows at an average rate of about 0.35 mm per day, which translates to roughly 0.5 inches (1.3 cm) per month or about 6 inches (15 cm) per year

. However, this rate can vary depending on factors such as age, genetics, sex, ethnicity, hormones, diet, and overall health

. The hair growth cycle consists of three main phases:

• Anagen (growth phase): Lasts 2 to 6 years (sometimes up to 7-8 years), during which hair actively grows. About 85-90% of hair follicles are in this phase at any time

• Catagen (transitional phase): A short phase lasting about 4 to 6 weeks where growth slows and follicles shrink

• Telogen (resting phase): Lasts around 2 to 3 months; hair stops growing and eventually sheds

Because hair grows primarily during the anagen phase, the total length hair can achieve depends on how long this phase lasts for an individual. For example, if hair grows about 1-1.5 cm per month, it would take roughly 8-10 months to grow 10 cm of hair, with some variation between men and women due to hormonal differences

. Ethnicity also influences growth rates: Asian hair tends to grow faster (up to 0.8 inch or 20 mm per month), while African hair grows slower (around 0.2 inch or 5 mm per month)

. In summary:

• Hair grows about 0.5 inch (1.3 cm) per month on average.
• The growth phase lasts 2 to 6 years, determining maximum hair length.
• It takes approximately 8-10 months to grow 10 cm of hair, depending on individual factors.
• Growth rates vary by genetics, age, sex, ethnicity, and health.

Thus, the time it takes for hair to grow depends on how much length you want and your personal hair growth rate, but generally, hair grows about half an inch per month