What Do the Numbers Inside Glasses Frames Mean?
The numbers inside glasses frames often describe three measurements: lens width, bridge width and temple length, in millimetres. They help identify the frame's size. They are not your prescription or your pupillary distance (PD).
If you are keeping your frames and replacing the lenses, these markings are useful details to share when asking about your pair. Here is how to read them without confusing frame measurements with lens-order information.
How to read 52 □ 18 140
For a frame marked 52 □ 18 140, the usual size sequence means:
| Marking | Meaning |
|---|---|
| 52 | Lens width: 52 mm across one lens. |
| 18 | Bridge width: 18 mm between the lenses above the nose. |
| 140 | Temple length: 140 mm along the arm that extends towards and behind the ear. |
A small square or dash commonly separates the first two measurements. Ray-Ban's size guide explains this sequence and notes that some frames show only the first two numbers. Check inside the arms for the markings; their position and format can vary.
Are these numbers my PD?
No. PD describes the distance between your pupil centres, while the printed frame numbers describe the glasses. Do not add lens width and bridge width together and enter the result as your PD.
ZEISS's explanation of individual lens fitting distinguishes PD from viewing height, which relates to where your eyes look through the lenses. A frame's printed size does not supply those personal fitting measurements or the prescription needed for your lenses.
Do frame numbers tell you which replacement lenses will fit?
The size sequence alone is not a complete description of a frame. For example, “52” gives a width; it does not describe the lens outline. Treat the markings as reference information, rather than a guarantee that lenses will fit.
With Dr. Lens Change, you send in your physical frames so replacement lenses can be prepared and fitted to your pair. See how lens replacement works for the ordering and shipping process. The frame eligibility guide explains the frame types accepted and details that may affect your order.
What if the markings have worn off?
You can still ask about your frames. Take clear photos of the front and side, plus a close-up of any markings you can read. Copy the visible text as it appears instead of guessing missing digits, and mention any damage or loose parts.
Contact our technicians about your frames if you are unsure what the markings mean or whether your pair is suitable. Frame numbers can help start the conversation; your actual frames and lens requirements determine the next steps.