Ring sizing is tricky, especially if the piece you’re getting made or buying is a surprise. If you’re off by even half a size, you’ll need to get it resized and depending on the style, that might not be possible or can weaken the ring’s integrity.
Tips n’ tricks
1. The engagement/wedding rings usually goes on the “ring” finger of the left hand. The left and right hands are not identical, and one hand will typically be half-size smaller than the other.
2. Ask a jewelry artisan they frequently buy from. I generally keep a log of my client’s ring sizes just for occasions like this! Sleuth level: Easy
3. If your partner already has a ring that fits their ring finger, bring it into a jeweller and get it sized (this is usually done free of charge.) Sleuth level: Medium
4. The printable ring sizers you find online are not always accurate. Email me and I will happily send you a plastic ring sizer. Don't be a creep, but while your partner is sleeping, size their finger with it. Sleuth level: Extremely High, only use this method if your partner sleeps like a rock and if it absolutely MUST be a surprise! Your best bet is to get the most accurate measurement possible. Being sneaky about it is commendable, but if you're way off, sometimes the ring cannot be resized. You can always just ASK your partner what their ring size is, or go to a jewelry store together to get sized. Trust me, it's still a surprise to get a ring regardless.