A giant congenital melanocytic nevus is usually of the size:
American National Institutes of Health (NIH) consensus definition to categorize naevi as small under 1.5 cm in diameter, large as having a diameter between 1.5 and 20 cm and giant naevi as having a diameter of 20 cm or more. Note: It is also called garment or bathing-trunk naevus. Most common site is lower back. Ref: Rook's textbook of dermatology, Edition-8, Page 54.10.
5-10cm
10-15 cm
15-20 cm
>20cm