If your mind is made up with a surprise proposal there are ways to figure out your significant others ring size. You’ve got to be cool and be subtle about it. Women are a lot smarter than we give them credit for sometimes. If you blow your cover, you’ll lose that OMG moment. Be cool. Ask her to help you pick out a ring for a sister, mother, grandmother or someone she knows. Ask to borrow her fingers and have her check some sizes for someone’s hand that is close to hers. You can casually ask her for your own reference what her ring sizes are and if you really got some nerve buy an inexpensive size 6 ring and have her try it on. Size 6 to 6.5 is the most common ring finger size for the average woman. You can tell her the ring is for your mother and actually give it to your mother so she won’t suspect anything. We will teach you how to secretly get her ring size.