Know your frame size while you’re on-the-go with your credit or debit card. Surprisingly, the standard width of the card can be compared to a medium (M) sized frame.
To measure, place one edge of the card at the center of your nose and see where it ends. If the card ends at the tip of your eyes, a medium-sized frame would fit you perfectly. If the card width extends the eyes, a small size would be perfect for you. Just in case the card edge finishes before your eyes end, you need a (L) large-sized frame