The ring would need to be cut down either half a size or one full size. It's also not cheap it's from Tiffany's
I was about to say "more than you paid for the ring" until I got to the Tiffany's part.
It varies greatly from one jeweler to another, and it depends on the ring too. Also, some rings can't be re-sized at all if they have stones, due to the way the stones are set, so keep that in mind. You could purchase a ring guard for it if that's the case.
It's best just to take it to a couple of reputable jewelers and ask what they charge.
