The standard gauge for a typical earring is usually 20g or 18g. However, if the earlobe was pierced by a professional, the gauge size may be 16g or 14g. According to Maison Miru, if a standard earring post fits snugly through the piercing, then the gauge size is 20g. Banter provides a gauge size chart for body jewelry, which shows that 20 gauge is equal to 0.812mm, and 18 gauge is equal to 1.024mm.