According to 39 Health Network, under normal circumstances, the thumb width of adult males is about 2 cm, and the little finger is about 1 cm, so the thumb diameter is 2.5 cm, and the adult thumb length is about 6 to 10 cm. If the congenital structure of the thumb grows abnormally, it will change the structure and easily cause the thumb to be relatively wide. If there is no discomfort, no special treatment is needed.