The gauge size of a standard ear piercing that accommodates standard earrings is 18 or 20 gauge. The size of the piercing and the size of jewelry used in the piercing is determined by the gauge; the higher the gauge number, the thinner the hole or piercing. A 20 gauge, or 0.81 millimeter, piercing is thinner than an 18 gauge, or 1 millimeter.
The standard gauge size determines the diameter of the piercing and the type of jewelry the piercing can accommodate. The 18 or 20 gauge piercing is generally the standard for ear and nose piercings used by professional piercers. Each person's body is different and various gauge sizes and lengths may be used.