1. Wrap string or paper around the base of your finger.
2. Mark the point where the ends meet with a pen.
3. Measure the string or paper with a ruler (mm) then divide by 3.14 (or Pi) to get the diameter of the ring.
4. Pick the closest measurement on the ring size chart to find your ring size.
More Ring Sizing Tips:
1. Measure the inside of another ring that fits using a tape measure and refer to a ring sizing chart.
2. The ring should fit your finger comfortably: snug enough so it won't fall off, but loose enough to slide over your knuckle with relative ease.
3. When the knuckle is bigger than the base of the finger, measure both places and pick a size in between the two.
4. Measure your ring size at the end of the day when your fingers are warm. Finger size changes depending on the time of day and the weather, and your fingers are actually smaller in the early morning and in cold weather. Also, keep in mind that fingers on your dominant hand are usually larger.
5. Measure 3 to 4 times for more accuracy.