While the numbers alone don't tell the whole story when it comes to finding the right size glasses for you - design also plays a big role role - the measurements of the frame and lenses are a useful tool to begin with. The single most important measurement is the overall width of the frames. Naturally, that width needs to accommodate your face comfortably. Your eyes should fall just about at the center within that distance. If the frames are too wide, they will make your eyes appear too close together. Similarly, frames that are too narrow will accentuate the width and overall size of your face. Proper proportions give your face a balanced look.