Use an existing ring that fits the intended finger
Place the ring on a strip of paper and mark where the inside edge completes a full circle
Measure the marked length in millimeters (circumference)
Use a ring-size chart to convert circumference to ring size
Alternatively, measure finger circumference directly:
Wrap a flexible measuring tape around the finger at the knuckle area where the ring will sit
Note the circumference in millimeters
Convert using a ring-size chart
Measure finger diameter directly:
Wrap a strip of paper around the finger and mark where it overlaps
Measure the length in millimeters
Use circumference-to-diameter conversion or a ring-size chart
Measure diameter using a ruler:
Lay the finger flat and measure across the widest part (millimeters)
Convert diameter to ring size using a chart
For accuracy:
Measure in the late afternoon or evening
Measure multiple times and use the average
Measure on the same finger and at the same knuckle level as the intended ring fit
If between sizes:
Choose the size that matches desired fit (snug vs comfortable) per your chart guidance