Use measurements from a pair that already fits
Most frames list three core measurements in millimeters. Compare them with a comfortable pair you already own instead of relying on style name alone.
The horizontal width of one lens. Common adult sizes often fall around the upper-40s through upper-50s mm, but fit depends on the entire frame.
The distance between lenses where the frame rests at the nose. Compare this closely with a comfortable existing pair.
The arm length from hinge toward the ear. Use it together with overall frame width and fit classification.
Use Narrow, Small, Medium, Wide, or Extra Wide as a quick starting point, then verify the actual measurements.
