Skin, Thick and Thin. Skin is generally classified as thick skin (on our palms and soles) and thin skin (on the rest of our body). With callouses, thick skin can reach thicknesses of nearly half an inch (13 mm). Thin skin varies in thickness from about 0.5 mm on the eyelid to about 2 mm on the back (1 mm is about the thickness of a dime). Skin is made up of three major layers called the epidermis, dermis, and hypodermis.