Sizing
The best way to find out your size is to use a sizer or go into a jeweller and ask if they mind measuring you up.
I use the British/Australian sizing (letters)
You can purchase a ring sizer in my store.
If you are buying a ring as a gift, if you can somehow do some sneaking and get ahold of a ring they wear already you can measure the INSIDE diameter across the widest point and let me know!