If you don’t already know your ring size, the best way to find an accurate measurement is to go to a local jewelry store and use a ring sizer. The right size should fit snugly around the finger while still being able to fit over the knuckle with relative ease. Make sure your hands are warm when measured; when your fingers are cold they are slightly smaller and won’t provide a comfortable measurement.
The profile of Haran varies from size to size. See below for reference. Top measures approximately 21MM x 9MM x 3MM.