It's easy to measure your ring size.
Pick the finger you want the ring to go on. Wrap a piece of string around it, not tightly, but snug and make a mark where the string meets. (Make sure the string you use is not elasticated). Shoe laces usually are, so they are not a good thing to use.
Lay the string along a ruler, using the metric side for accuracy.
If it comes out to 57mm for example, that is equivalent to US Size 8.
Cut a thin strip of paper, if you don't have string at hand.
Repeat it a few times, just to be sure.
See our Ring Size Chart for further details.