The Hamilton-Norwood scale is a way of measuring male pattern baldness. It was introduced by Dr. James Hamilton in the 1950s and later revised and updated by Dr. O'Tar Norwood in the 1970s..
Level 1: Full head of hair with no visible signs of hair loss.
Level 2: Hair starts to recede around the frontal region of head.
Level 3: Hair recedes deeper into the frontal and temporal regions. Same pattern as Level 2, but more visible.
Level 4: Hairline has drastically receded in the frontal and temporal regions. There is beginning to show balding in the parietal region.
Level 5: The same pattern of baldness as in level 4 but there is a decrease in hair density.
Level 6: The strip of hair that once connecting the two temporal regions of the scalp is no longer visible.
Level 7: The hair has receded all the way to the occipital region of the scalp and the temporal regions no longer have hair.