Finding out my boyfriends ring size?

Breanna • 28 years old, lost my first baby 💔 12/11/17 - 1/31/18 👼 Married💍 Mama 👩‍👧

My boyfriend and I will be together for 2 years in November and I want to buy him a ring for his anniversary gift. Problem is I cant remember his ring size. Any tips on how to hint about his ring size without giving it away?