Before placing the order, you will need to figure out here exact ring size. Below are some tips that should help.   Sneak Out an Existing Ring This is a foolproof way of getting the right ring size. However, you should be sure it is a ring, which she wears on the same finger as that one intended for the engagement ring. Get access to her jewelry box and pick a ring that she wears on the left hand. Borrow this ring without her knowing, and either get it to an expert to find out the size, or do it yourself. How to Do it Yourself Take a printout of a ring sizing sheet, and place the ring on the sheet. If you don’t have the time it takes for this, then put the ring on your own finger, and watch how far it slides till its snug. Mark that point, and you will know what size of the diamond ring to get for her.