Frame Measurements
There is no one "right size" of glasses. Your face can accommodate a wide variety of glasses sizes and many eyewear frames will work for most people.
"Size" in glasses is a completely different concept than "size" in clothing or footwear. As a result, your focus should be on how the glasses look on you; when we find glasses that look good, usually the glasses can be adjusted to fit your face.
Glasses size
An eyewear or sunglasses frame model is usually available in just one "size", meaning one combination of eye, bridge, and temple lengths. Occasionally a glasses frame may have multiple sizes: for example 50-17-135, and 52-17-135, and 54-18-140. These measurements specify the proportional dimensions of the frame.
Measurements
Glasses frames have four basic measurements: the lens width, bridge, temple, and lens height measurements.
The Lens Width (eye size or A measurement) refers to the horizontal width in millimeters of one of the frame's lenses.
The Bridge Width measurement is the distance in millimeters between the two lenses.
The Temple Length is measured along the length of the temple, from one end to the other, including the bend. Please note, in sunglasses with a wrap design, the wrap curve has the effect of bringing the frame front back towards the ears, thereby requiring shorter temples lengths to compensate.
The Lens Height (or B measurement) refers to the vertical height of an eyeglasses lens.
The B measurement is only important in regards to bifocal, trifocal, or progressive lenses.
Reading your glasses size
Most glasses frames have some size information printed on the inside temple of the frame. This lettering can wear away with use. To find all the lettering, you must look on the inside of both temples, and on the inside of the bridge.
The following is an example of eyewear specifications:
Eye
Bridge
Temple
Brand/Model #
Color #
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52
19
135
RB201
635
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In this case, the brand RayBan is abbreviated RB, followed by the model number of the frame. The eye size is followed by bridge size, sometimes with a small square box in between. The temple length could be printed after the eye and bridge sizes, or elsewhere. Other letters and numbers usually refer to the color of the frame. The B measurement is not on the frame.
Total Front glasses width
However, these sizes do not give you all the information that you need to know for sure how "big" the glasses frame is. To know truly how big the frame is - meaning how it will look on your face - you must determine the total frame width.
Once you have determined the total frame width, you can compare to your current glasses, or you can hold a ruler up to your face to get an idea how well the frame will line up with the sides of your head. Additional endpieces that are used to mount the temples to the eyewire rim of the frame usually adds about 10% of the total frame width. You can quickly estimate the total frame width by adding the left and right eye size and the bridge size, and then multiplying times 1.1. Here is the formula to determine the total glasses width:
Total frame width = (left eye size + bridge size + right eye size) x 1.1 for endpiece
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