Are you thinking of popping that all important question soon, but don't know your girlfriend's ring size? Finding your girlfriend's ring size for purchasing an engagement ring can be nerve wrecking because you don't want her to figure out what you have in store.

There are a few subtle ways that you can start narrowing down her ring size, but it will take a little bit of time and effort on your part. Of course, you could just ask your girlfriend what her ring size is, but that would ruin the surprise, so try to find her ring size without such a straight forward approach.

Scope out her ring collection now.
If your girlfriend already wears rings, then it may be pretty easy finding her ring size. Start observing her hand jewelry and look for a ring that she typically wears on her ring finger or the opposite ring finger. Sometimes women wear rings on all fingers, which are different sizes, so you want to observe the rings that she wears on her ring fingers and not her middle finger or pinky. Now once you've narrowed down the ring, when she is in the shower or sleeping, discreetly take the ring and trace it onto a piece of paper. Trace the inside of the ring and the outside of the ring. From the tracing of the ring a jeweler should be able to figure out what size she wears.

The fake a ring purchase challenge.
If your girlfriend does not wear rings, then you may have to make an extra effort to figure out her ring size. The next time you and your future fiancee are out and about and you happen across a jewelry store or even a fun accessory store, tell her that you are thinking about getting your mom or sister a ring for their birthday. Make sure that your mom and sister wear jewelry and that you often buy them gifts -- otherwise she may get a little suspicious. Have her try on some rings for fun and actually buy something for your mom or sister so she won't get too suspicious.

Enlist the help of a trustworthy friend.
If asking her to try on rings is a little telling, then you should consider enlisting help from a trusty friend. If your sister or a girlfriend of hers can keep a secret, then let them know that you are planning on shopping for an engagement ring soon. Once they get over their excitement, tell them that they will need your help. Ask them to take your girlfriend shopping and nonchalantly go try on rings for fun. A planned out scenario might be fun, like if your sister is hoping that her boyfriend will propose, maybe she can mask the impromptu engagement ring interest as her own.

If all else fails, you can try to guess what her ring size is. The average woman's ring size is 6-7, so if your girlfriend is average height and weight, then she may be a 6.5. If she is above average or below average, then adjust accordingly. Also, before purchasing the ring, speak to your jeweler to make sure that you will be able to re-size the ring if it is too big or too small. It is better to know upfront about any additional charges - just in case.