How do you order a ring for someone when you don’t know his or her ring size? The handy Israeli app Findmyringsize will tell you. Take an existing ring and hold it over the images on your smartphone or re-sized computer screen. Simple to use and you could make someone very happy.
http://findmyringsize.com/
http://www.beckysbeautytips.com/2014/01/26/an-innovation-for-measuring-your-ring-size/