What do the numbers on glasses mean?

Most frames have three numbers printed inside the temple, such as 52–18–140. They describe dimensions in millimeters—not a guarantee that the frame will fit your face.

Lens width: 52 mm

The first number is the horizontal width of one lens opening, measured at its widest point.

Bridge width: 18 mm

The second number is the distance between the two lens openings. Actual nose fit also depends on the bridge shape and nose pads.

Temple length: 140 mm

The third number is the length of the arm extending toward your ear. It does not directly tell you the total width of the front of the frame.

Why total frame width matters

Two frames marked 52–18–140 may have different overall widths because of rims, hinges, and shape. Compare the retailer's published total frame width when available.

Typical ranges for adult frames

Lens widths commonly run from the low 40s to the high 50s in millimetres, bridge widths from about 14 to 24 mm, and arm lengths from 130 to 165 mm across the 150 frames we list, with 135 to 145 mm the most common. These are broad ranges for orientation, not a recommendation. Your own best numbers depend on your face and nose.

How to read the numbers on a pair you own

1. Open the arm and look on the inside near the hinge. Some brands print the numbers on the bridge instead.
2. You may see two or three numbers separated by a square, a dash or a space. The first is lens width, the second bridge width, the third arm length. A model code or colour code often sits next to them.
3. If you wear a pair that fits well, write the numbers down. They are a good reference when you compare frames online.
4. Measure the total width across the front with a ruler. It is the one number the marking does not give you.

Lens height and fit

Many stores also list lens height, the vertical size of the lens opening. It affects how much of your cheek the frame covers and how much room a progressive or bifocal lens has. Ask an optician what height your prescription needs; do not choose it from a chart.

Try frames on your face

Use FitMyFace's free glasses finder to compare estimated sizing across retailers. Virtual measurements are approximate and should not replace an optician's final fitting or prescription pupillary-distance measurement.

Having trouble with slipping frames? Read our low-bridge fit guide. Not sure which frame shape to start with? See glasses for every face shape. Need the total width of a pair you own? See how to measure frame width at home. Choosing between frame types? See rimless vs semi-rimless vs full-rim glasses.

Already know the three numbers on your current pair? Search the public retailer listings by lens width or a size such as 52–18–140. A listed lens number is not a promise of face fit or of a retailer having that frame in stock.

Questions

Do the three numbers tell me if a frame will fit?

They help, but they are not enough. Lens, bridge and arm length leave out the rims and hinges, so they do not equal the total width across the front.

Which number matters most for comfort?

It depends on the problem. Total frame width affects pressure at the temples, bridge shape affects slipping, and arm length affects how the glasses sit behind the ears. An optician can check all three.

What if my numbers are not printed?

Look at the other side of the bridge, or measure the lens opening, bridge and arm with a ruler. Estimates from a ruler can be a millimetre or two off.

Sizes are estimated from a photo, and the on-face drawing is approximate. It is not a substitute for an optician: let an optician confirm your prescription, pupillary distance and final fit. The ordinary glasses scan runs on your device. The optional AI previews (hair and glasses) send a photo to Cloudflare; your consent is the one "I agree" on the scan screen, and a switch on the results turns them off. FitMyFace is for adults 18 and over and is not available in Illinois.

To see frames grouped by total front width across stores, use the frame pages by width and shape.