Ring Sizes
If you’re purchasing a ring on the internet, trying it on in advance is obviously not practical. Fortunately ring sizes are fairly well standardized, and should not be much of a problem if you know your correct size. Wikipedia has an excellent chart showing various ring sizes with their standard and metric equivalents:
http://en.wikipedia.org/wiki/Ring_sizes
Wrapping a piece of sting or a stip of paper around your finger should provide you a good starting point in determining your ring size. For instance, if a piece of string 2 inches (52mm) long fits well around your pinky finger you could estimate you’d need around a size 6 ring. However you should keep in mind that your fingers swell at different times of the day and take that into consideration. For the best fit, it’s wise to visit a jeweler and try a professional ring sizer. If you do purchase a ring that doesn’t fit quite right most jewelers can easily resize it for you at minimal cost ($20-40), and they don’t care if you purchased it their store or not.
The average man’s pinky finger is usually around a size 8.