A big part in the overall look and comfort of your eyewear is getting frames that fit excellently in every aspect. Like finding the perfect pair of flattering and super comfortable denim, you’ll need to determine not just one, but several measurements to find the frames that fit like they were made especially for you. Here’s all you need to know.

How to Determine Frame Measurements

All glasses frame manufacturers use a standard set of three measurements in millimeters to specify the frame dimensions. It’s the same for sunglasses. These will be indicated with three numbers, most often located inside the arms (temples) of the glasses. Occasionally the size is labeled on the bridge. Those three numbers correspond to the following:

1. Lens width (31 - 60mm): Length across the top of the lens.
2. Bridge width (12 - 31mm): Length separating the two lenses across the nosepiece.
3. Arm (temple) length (115 - 155mm): Length spanning the hinge of the arm to the tip of the earpiece.

Now that you know the system and what these numbers describe, we’ll proceed with how to identify the fit that works for you...