Welcome to The Silicone Ring Store
There are a variety of ways to determine your ring size.
Here's the option we recommend. You will need a pen, string or a piece of dental floss, and a ruler.
Size 8: 18.14 mm / .0714 in
Size 9: 18.95 mm / .0746 in
Size 10: 19.76 mm / .0778 in
Size 11: 20.57 mm / 0.810 in
There are other ring-measuring techniques on the web if this didn't help.