The most common measurement used in classifying the level of hair loss in men is the Norwood Scale (or Hamilton-Norwood Scale).
The Norwood measurement system ranges from a level one, which represents little to no hair loss, to a level 7, which is characterized by severe baldness where only a rim of hair remains.
Hair loss in men can be caused by many factors, but the number one reason men lose their hair is due to a hereditary condition called Male Pattern Baldness or Androgenic Alopecia.
This type of hair loss is responsible for about 90% of hair loss in men.
The result is ordinarily a receding hairline or thinning hair at the top of the crown of the head. Though most men fail to recognize the issue until 50% of their hair has already been lost.