Put a ring on it? There’s an iPhone app for that, thanks to Tiffany. Today, Tiffany & Co. launches its brilliant (free) Engagement Ring Finder iPhone app, which lets you not only browse engagement rings and share your favorites with friends (or lovers), but also lets you (or him) determine your ring size. The ring sizer is the first of its kind and our favorite feature — simply place an actual ring on the screen and voila, you’ll find out the size. Proving, once again, that size does matter. So whether you’re dreaming of being a bride or you’re a guy trying to surprise the future missus, Tiffany & Co. has you covered, daaahling. Where to get the free app? Right here.