Borrow from their jewelry box & bring it into a jewelry store (including ours!)
Let the professionals do it for ya :)
Can't sneak one away without them noticing? Take a picture of it next to a ruler OR press it into a bar of soap and bring in the soap.

Measure their finger while they're sleeping
Get a ring sizer here!
An easy and for-sure way to find the right fit for their finger!

1. Pull the end of the sizer through the buckle, keeping the number side facing out
2. Put the loop on the finger you intend to wear the ring
3. Tighten the buckle - this is the most important step, make sure that you can take the sizer on and off comfortably and that it's not too tight or too loose. You should feel a little resistance at the knuckle but it should come on and off easily. Adjust until you find the perfect fit!
4. Read between the lines - remove the sizer and the arrow should point to your size. We currently offer full sizes for rings - so adjust to find the most comfortable fit for your finger within those ranges and you are G2G.

Enlist some accomplices to ask, so it won't ruin the surprise
Besties helping besties!

Draw a line where their ring sits on your own finger and then measure with a piece of string, floss, or strip of paper
Simply wrap your string, floss, or paper around your finger and cut right where it overlaps OR mark it with a pen. If you're using paper, try to keep it to under a half inch in width for more accurate results. Nudge that baddie up against a ruler, and match your results with the following:

46.8 mm = Size 4
49.3 mm = Size 5
51.8 mm = Size 6
54.4 mm = Size 7
56.9 mm = Size 8
59.5 mm = Size 9
62.1 mm = Size 10
64.6 mm = Size 11

Get a wax hand?
Probably the funniest suggestion yet, but what about taking them to one of those places where they do wax figures? Ask the staff to measure the fingers "as part of the process" and tada! Now you know 🤭