Find Your Eyeglass Size
How do you know what frame size to wear?
The easiest way, if you currently wear glasses, is to look for that size information on your current eyeglasses. Either marked on the temple on your frame or on the bridge of your frame will be some numbers which will look something like this 52☐17. The first number is the width of each lens, the second number is the distance btween the lenses, also in millimeters. Most frames have the "box" between the numbers, this indicates the lenses are measured with a boxing system.
This numbers don't mean that only a 52☐17 will fit you, think of these sizes as merely guidelines. A millimeter or two difference will not make that much of a difference in fitting. The frame sizes are measured in such small units because that is necessary for the accurate placement of prescription lenses into the frames.
If you do not currently have glasses or cannot read the numbers on your frame you may want to visit an optical shop to try a few on. Make note of the frame sizes that seem to be a comfortable size.
In general any frame with a lens measurement of 49mm to 52 mm would be an average size. Lens sizes less than 49 would be a better choice for narrower fits. Lens sizes avove 52 would be a better choice for those requiring a larger frame.
So remember your own sense of style will determine if you like larger or smaller frames but following these guideline will allow you to find frames that fit.