Get the right size the first time! There is really only one way to get a truly accurate rig size, and that is by trying on a ring style sizer.
Paper strips, adjustable gauges, calipers, tape measures... NONE of these will work, and are usually off by at least half a size, trust me, I do this for a living.
These are available as a service to my customers as an easy and convenient way to get the proper size with out having to go to a jewelry store. I am selling these at cost, to make sure that you get the right size ring.
Will fit fingers from size US 4 - 13, including half sizes. Each gauge is clearly marked. Use this tool again and again with everyone in your household.
Important: If you are planning on purchasing a wider ring, such as 6mm or wider, than keep in mind that a wide ring will feel tighter than a narrow ring, so plan on ordering at least 1/4 to 1/2 sizer larger than the reading you get from these narrow gauges.