If you don't already know your ring size, that isn't a problem as I have these handy ring sizers available to purchase. Inexpensive and easy to use, simply wrap around your finger and read your size.
How to use:
Firstly, thread the end through the loop at the opposite end and pull reasonably tight to fit over your knuckle of the finger you wish the ring to fit (but not so tight it won't move). You then want to slide the sizer down your finger and see how it feels for fit. You want your ring to fit so that it is neither too tight, nor too loose and the ring sizer should be able to slide back up over your knuckle. One tip, try to keep the sizer as round as possible, don't distort the shape by squeezing it.
You may find this YouTube clip useful: How to Use the Multisizer Ring Sizing Gauge - YouTube
I post within the UK, as well as the US and Canada.
UK - orders over £50, FREE Royal Mail Tracked
UK - orders under £50, Tracked 24
US and Canada - Royal Mail International Tracked