What Are the Numbers on Eyeglasses?

Most optical measurements are done in millimeters. You might see identifying numbers on the temple, or "arm" of your eyeglass frame or sometimes on the bridge, the nose. The numbers on your eyeglass frame reflect specific information about the frame size, model, style, colors and other information for the optical lab to use to make your eyeglasses.

Lens Size

• The front part of the frame is called a chassis or frame front. One of the numbers on the frame that the optician uses is the lens size. The numbers you see might be written in a format similar to 48 x 22 x 145. The 48 is the lens size and averages 35 mm up to 54 mm but can be smaller or larger depending on the style.

Bridge Size

• The bridge of a frame rests on your nose. In the example 48 x 22 x 145, the number 22 is the bridge size, which can range from 16mm to 26 mm but can be smaller or larger.

Temple Size

• In the example 48 x 22 x 145, the temple is 145 mm long, a standard temple size according to the optometristsattic.com. Older, retro style frames were measured in inches, so you might find a temple with numbers that read "4 1/2" or "5," but they are not common anymore. Temples can be as short as 135 or as long as 155 mm, depending on the size of the frame.

Other Numbers

• Frames almost always have other numbers on the inside of the temple that help define the manufacturer, model, size and color of the frame. Each frame manufacturer uses its own system, so the numbers vary.