Measure the inside diameter of the ring in millimeters using a ruler or calipers
Measure the inside circumference by wrapping a flexible measuring tape or strip of paper around the ring’s inside edge, then measuring the length in millimeters
Use an existing ring that fits well and match its size on a ring size chart (diameter or circumference)
If measuring with paper or string, mark where the ends meet, then measure the marked length in millimeters
Convert measurement to ring size using a standard ring size chart (US, UK, EU, or other system)
Measure multiple times and use the largest consistent measurement if results differ
For best accuracy, measure in the temperature range when fingers are typically neither swollen nor shrunken
If between sizes, choose the larger size for comfort or the smaller size for a snug fit (based on preference)
If ordering online, verify the retailer’s size chart and conversion method before purchasing
Consider re-measuring if the ring is worn on a different finger or if the fit feels different than expected