How to determine your platinum ring size:
A lot of people don’t know their ring size. Here are some tips for guessing her ring size, or learning the exact size by comparing to an existing ring that fit

• Guessing your ring size :
  The average woman’s ring size is 7, and this would be for a woman who is 5'4" and weighs about 155 lbs. However, finger shape and size differs greatly among people. Given the same weight, taller people generally have more slender fingers. If she is 5'4" and weighs 200 lbs, her ring size is probably 9. If she weighs 130 lbs, her ring size is probably 6. If you guess wrong, many local jewelry stores can size a family ring while you wait, and the average charge is about $20 to take a ring up or down a size.
  
• Measuring from an existing ring :
  If you have an existing band that fits (but you don’t know the size), then print out the file on this page of platinum ring sizes and place the band over the circles below. Choose the size of the circle that best fits the inner edge of the actual band.
  
• Measuring from the ring finger :
  If you can actually measure from the ring finger, then print out the file on this page of platinum ring sizes and cut out the paper strips for each ring size. Wrap the paper strip around the ring finger (make sure to allow room for the ring to pass over the knuckle). The exact measurement for each ring size is shown on the paper strip. Measure the distance with a ruler and mark the actual size shown on the paper strip.