What is the average growth rate of healthy scalp hair?

The average growth rate of healthy scalp hair is typically about 1 inch per month. This rate can vary based on several factors, including genetics, age, and overall health, but the general consensus in the field of hair science is that hair grows approximately 0.5 inches to 1 inch per month.

When considering the other options, it's important to note that while some sources might suggest 1 inch in 2 months or 1/2 inch per month, these don't represent the average growth rate. The option of 2 inches per month is much higher than what is typically observed and is not supported by standard measurements of hair growth. Thus, the figure of 1 inch per month is recognized as the standard average growth rate for healthy hair on the scalp.