This is a table to help you find your size.
Measure the circumference of the finger you want to wear ring, and choose your ring size based on the circumference.

HOW TO MEASURE YOUR FINGER:
Find a piece of paper (no wider than 3/4") or string long enough to wrap around the finger on which you will wear the ring. Wrap the piece of paper or string around the base of the appropriate finger tightly, but comfortably, and with enough room to slide over the knuckle. Mark on the paper or string where the two pieces come together and overlap. With a ruler, measure the distance between the marks and use the size chart to find your ring size.