Don't know your size?
Step 1: Wrap a thin piece of paper around your finger like a ring. A ring should fit secure enough so that it will never fall off. It should have a loose comfortable fit when sliding it over your knuckle.
Step 2: Mark the spot where the paper meets, and measure the distance using a ruler.
Step 3: Use the chart below to match the ring circumference (in mm) to the ring size (in US).
Ring Conversion Chart