Measure the inside diameter of an existing ring in millimeters
Use a ring-sizing chart to convert inside diameter to ring size
Measure your finger circumference in millimeters with a soft measuring tape
Use a ring-sizing chart to convert finger circumference to ring size
Measure circumference using string or paper, then measure the length against a ruler
Consider measuring at the end of the day when fingers are slightly larger
Measure twice or three times for accuracy
If between sizes, choose the larger size for comfort unless the ring is adjustable
Check sizing for the specific country/standard (US, UK, EU, AU, etc.)
If ordering online, use the retailer’s printable ring sizer or sizing tool
If possible, ask a jeweler for sizing using a ring mandrel or sizing gauge