This is the width/diameter or a single strand of hair.
Hair diameter ranges from fine - medium - coarse.
The is a common misconception that black hair is coarse when it is actually the opposite most of the time.
In numbers .06 - .08mm in hair width is considered medium. since chances are we can not measure a single strand of our hair there is two tests to help determine your hair diameter.
Test 1: place one strand of hair in between two-finger. Now slide down the length of your hair. if you barely feel anything there then your hair is fine and if you do feel it then it is coarse. Since then is hard to compare there is another test to determine.
Test 2: Strand test
With this, you need one strand of your hair that can use shredded hair and one piece of thread(such as seeing thread). Placing them next to each other compare the width. If your hair is thinner than the thread then your hair is fine. If it is wider then your hair is coarse. If it is the same width then yours is medium.
What is your hair diameter?