Ring Size Guide Step 1: Prepare a slip of paper. Draw then cut out a T-shape with a small rectangular hole. Make sure the end could pass through the hole. Step 2: Thread the end through the hole. Put and fasten it just right on the finger. Fold in the opposite direction. Step 3: Measure from the length of the rectangular hole to the folded line. Check out your finger size according to the mm measured. Ring Size Chart