Confession: When I signed up for Hatch's Ambassador membership, I didn't know my ring size. (Does this make me weird? Am I randomly supposed to just know this?) Since I didn't know how to measure for it either, I just guessed.
Turns out there's a better method:
1. Wrap a thin strip of paper around your finger (like a ring).
2. Mark the spot where the meets, and measure the distance with a your ruler.
3. Use the nifty chart below to determine your ring size.