...The best way that I know of to get the correct finger size for that Engagement Ring is to
ask her Best Friend and if that doesn't work,
ask her Mother!
BUT, you've got to get them to swear to total confidentiality! Once they know it's an Engagement Ring and a proposal is coming, they'll zip their lips quicker than you can say "Zip it!"
No doubt that they have gone into Jewelry Stores in the past just to browse the Wedding Rings, Engagement Rings and Solitaires! I've seen it happen daily. Women just have to look. It's built in! They do!
Woman have gone into Jewelers trying on countless Engagement Rings and store things into memory, like what size her Best Friends ring finger is. I'm serious. Women do this. If you ask her Best Friend I'm sure, under normal circumstances, she'll be able to tell you without batting an eyelash.
They do that Just in case!
They've been looking forward to this all their lives and Women are always prepared for anything. And in fact, even under the slight chance that her Best Friend or Mother doesn't know the exact size, they are better off than anyone at guessing! Plus Women always try on each others rings. They do these things. They just know! Trust me.
You'll get her ring size, she'll be surprised and you both will live happily ever after! I'm crossing my fingers on this one. And believe me, Women LOVE surprises! So don't ruin this for them.
Some guys still want to try the old trick of tying a string around her finger while she sleeps. Give it up. That string really won't help a jeweler out when it comes to fitting a metal band. Plus, she'll probably wake up.
And there's more important things you should know about her finger size...