The better your frames fit, the better they flatter your face. Consider searching for your glasses as you would for a pair of shoes – first, you need to know your size.
Frame size incorporates three key figures, all of which are measured in millimeters.
Lens width: Between 31-60 mm
Bridge width: Between 12-31 mm
Glasses arm length: Between 115-155 mm
It’s easiest to find a pair of glasses that fit you already — whether they’re your current prescription pair, a set of sunglasses, or even your friend’s glasses (if you don’t yet have your own), and get the sizing from there. Usually, the frame manufacturer prints the size numbers on the inside of the arm of the glasses. Sometimes they’ll print them on the bridge. See the above image for reference.