if you’re in Toronto, come visit me at the studio for a proper ring sizing - if you’re not local, the next best option is to visit a local jewellery store and consult with a knowledgeable employee
I also offer complimentary ring sizers - get in touch with your address, and I will put a stamp on it and send it through regular mail, along with some tips for sizing yourself
a less reliable option - take one of your own band rings and visit www.findmyringsize.com and make sure to select US sizing/band ring (I say this is less reliable because different screens/resolutions may alter your final results)
another less reliable option - wrap a piece of paper around your finger and tape it where it overlaps, cut it open and then measure the length