Glasses frames are sized with three numbers, usually printed inside the temple arm: lens width, bridge width and temple length in millimeters. In 52-18-140, the lenses are 52 mm wide, the bridge is 18 mm and the arms are 140 mm long. The easiest way to find your size is to copy the numbers from a pair that already fits. Total frame width should roughly match the width of your face.
Frame size decides whether glasses sit comfortably, stay put and look balanced on your face. Here is how sizing works.
The three numbers
Inside one temple arm you’ll usually see something like 52□18 140.
| Number | Measurement | Typical range |
|---|---|---|
| 52 | Lens width | 40 to 62 mm |
| 18 | Bridge width (between lenses) | 14 to 24 mm |
| 140 | Temple length (arm) | 120 to 150 mm |
Some frames also list lens height, which matters for progressive lenses (usually at least about 28 to 30 mm).
Find your size
The best method: copy the numbers from glasses that fit you. Stay close:
- Lens width: within about 2 mm
- Bridge: within about 2 mm
- Temple: within about 5 mm
No glasses? Measure your face from temple to temple, or use a retailer’s virtual try-on and size guide.
Total frame width
Total width (across the front) should roughly match your face width. Frames that are too wide slide down; frames that are too narrow pinch at the temples.
Fit checklist
- Your eyes sit near the center of each lens.
- The bridge rests evenly without pinching or sliding.
- The frame doesn’t touch your cheeks when you smile.
- The arms go straight back and curve comfortably behind the ears.
- Glasses don’t slide when you look down.
Nose pads vs no nose pads
Adjustable nose pads help with low or narrow bridges. Frames without pads, common on acetate frames, fit best if the bridge shape matches your nose. Some brands offer “low bridge” or “Asian fit” versions.
Face shape (a starting point)
- Round faces: angular or rectangular frames add definition.
- Square faces: round or oval frames soften angles.
- Oval faces: most shapes work.
- Heart-shaped faces: frames wider at the bottom, or light rimless styles, balance a wider forehead.
Common questions
What does 52-18-140 mean on glasses?
52 mm lens width, 18 mm bridge width and 140 mm temple (arm) length.
How do I know my frame size?
Look inside the arm of glasses that fit you well and copy the three numbers. Stay within about 2 mm on lens width and bridge, and within about 5 mm on temple length.
Do frames come in small, medium and large?
Many brands group frames by total width. Roughly, under 130 mm is small, 130 to 140 mm is medium and over 140 mm is large, but always check the measurements.