We use the standard US ring sizing guide for our numbered sizes (7, 8, 9 etc).
Miansai has two options to determine your size.
First, we offer a Ring Try-On Kit that lets you see all of our different ring options and finishes and includes a ring sizer to determine your size. The price of the kit can be put towards the purchase of your ring.
Second, we offer the ring sizer by itself so you can determine your size.
You can find more information about your size here: http://ringsizes.co/