What is the standard hoop earring size in millimeters?

The standard hoop earring size in millimeters is 20 to 30. At this size, hoops will be between the size of a penny and a half dollar. Some makers offer hoops in sizes as small as 6 to 8 millimeters and as large as 70 millimeters or more. On 1stDibs, explore a diverse assortment of hoop earrings.