How do you find another person's ring size -- discreetly?

Question

How do you find another person's ring size?

Answer 1

You can ask her playfully or ask help from others like friends,relatives or family. Measure his/her finger when asleep. Using a play dough is also effective.

Answer 2

Check it when she's asleep.

Playfully wrap a thread around her finger and note the circumference of her finger in term of the length of thread stubly.

Measure from any previous rings she wears.

Just get her the ring and then you can get it exchanged later if it doesn't fit.