Glasses frame size guide: lens, bridge and temple
Look inside the arm of your glasses and you will find three numbers such as 52-18-140. They are the frame’s size in millimetres: the lens width, the bridge width and the temple length. This glasses frame size guide decodes them, tells you whether the frame is small, medium or large, and compares its width with your face.
Type the numbers (or paste them), add your face width if you want a suggested width, and read the result. It works in your browser and the face measurement never leaves it. For lens fitting you will also need your pupillary distance; see the pupillary distance calculator.
How to use the Glasses Frame Size Guide
- Read the numbers on the inside of the arm, or paste them into the box.
- Add the lens height for the drawing, and a measured frame width if you have a ruler.
- Measure your face width across the widest part with a ruler held flat, and enter it.
- Read the size class and whether the frame is narrow, a good fit or wide for your face.
- Use the suggested lens width range when shopping for a new frame with a similar bridge.
Glasses Frame Size Guide features
Decodes the numbers
Lens width, bridge width and temple length explained, in millimetres.
Size class
Small, medium or large from the lens width.
Face check
Frame width against face width with a good-fit window, and the lens width range that matches it.
Scaled drawing
A front view of the frame drawn from your numbers.
What the numbers mean
The numbers follow the boxing system standardised in ISO 8624, which describes a frame by rectangles drawn around each lens: the horizontal lens size, the distance between the lenses and the overall length of the side (ISO 8624:2020; read 19 October 2026). In practice that gives the three printed numbers: lens width (about 40 to 60 mm), bridge width (about 14 to 24 mm) and temple length (about 120 to 150 mm, commonly 135, 140, 145 or 150 mm).
Retailers such as EyeBuyDirect classify lens widths up to 50 mm as small, 51 to 54 mm as medium and wider than 55 mm as large; this tool treats 55 mm as large, because that source does not define it. Frame width, the full width across the front, is not printed on the arm; it is roughly twice the lens width plus the bridge plus the rims, and this tool adds 10 mm as an estimate unless you measure it.
Choosing the right width
Guides advise a frame slightly wider than your face, with no more than a finger’s width between the temples and the arms. A frame that is too narrow pinches the temples and makes the face look wider; one that is too wide slides down and makes the face look narrower. This tool treats a frame 0 to 10 mm wider than your face as a good fit, up to 20 mm as slightly wide, and anything more as wide. Those windows are rules of thumb, so try frames on or visit an optician, and remember the bridge must also sit comfortably on your nose.
| Lens width | Class | Example frame | Estimated frame width |
|---|---|---|---|
| 48 mm | Small | 48-19-135 | 125 mm |
| 52 mm | Medium | 52-18-140 | 132 mm |
| 56 mm | Large | 56-18-145 | 140 mm |
Limits
Frame sizes are not perfectly consistent between brands, and the shape of the lens and the thickness of the rim change how a frame looks. Progressive and bifocal lenses also need enough lens height. A kids’ or very large face may sit outside the ranges used here. For other sizing jobs try the clothing size converter and the ring size chart.
Glasses Frame Size Guide FAQ
What do the numbers on glasses mean?
The first is the lens width, the second the bridge width and the third the temple (arm) length, all in millimetres. For example 52-18-140.
What size are medium glasses?
Lens widths of about 51 to 54 mm are usually called medium; up to 50 mm is small and over 55 mm large.
How do I measure my face for glasses?
Hold a ruler flat across your face at the widest part, temple to temple, just below the eyebrows. Choose a frame about the same width or slightly wider.
Is frame width printed on the glasses?
No. Measure across the front of the frame with a ruler, including the hinges, or estimate it as twice the lens width plus the bridge plus a centimetre.
Which temple length should I choose?
Most frames use 135, 140, 145 or 150 mm. Pick the length of glasses that already feel comfortable, so the tips reach just behind your ears.
Can I use the numbers to buy online?
Yes. Matching all three numbers of a pair that fits you is the surest way, though shape and brand can still change the fit.