Many online jewelry websites offer complimentary mail order ring sizing kits. Often times, people place an order for a ring but have no idea what size of ring is needed to fit their finger.
Several online sites now offer a special package that they will send you in the mail, many free of charge, to use to measure your finger precisely. Of course, these sites most likely will ask you to order your ring first, but will hold off completing your order or mark it as pending until you have received your ring sizing kit and are able to add the ring size to your purchase information.
Something like this may be beneficial to those who can't see an actual jeweler for ring sizing or aren't able to get a good measurement by using other methods.