Norwood scale (Norwood-Hamilton scale)

The Norwood scale (Norwood-Hamilton) is the standard visual classification of male pattern hair loss. James Hamilton developed the original scale in 1951; O’Tar Norwood revised and expanded it in 1975. Variants and intermediate categories (e.g. Norwood 3 vertex) have been added since.

The seven main stages:

• 1: No visible recession.
• 2: Mild bitemporal recession; the “mature” hairline.
• 3: Deeper bitemporal recession; the start of clinically meaningful loss.
• 3 vertex: Norwood 3 plus thinning at the crown.
• 4: More pronounced recession plus a defined crown thinning area, separated by a bridge of hair.
• 5: The bridge of hair between the front and crown narrows.
• 6: The bridge breaks down; the front and crown losses connect.
• 7: The classic horseshoe of advanced loss; only a band of hair remains around the back and sides.

Used in clinical assessment, treatment decisions, and trial reporting. Photographic standardisation matters: same scalp area, same lighting, same angle, monthly, makes Norwood staging more reliable than impression-based judgement.