Most glasses have three numbers printed on the inside of an arm, such as 52□18 140. They are the lens width, the bridge width and the arm length, all in millimetres. If your current glasses fit well, these numbers are the quickest way to find new frames that will too.
Enter your numbers below to see your frame size and frames from opticians with high street stores that match it.
Find frames in your size
Use the numbers on your current glasses. Nothing you enter is saved or sent anywhere.
Enter at least the lens width and bridge to see frames in your size.
A guide only. Sizes come from Vision Express and Ace & Tate product pages, which list measurements, and were checked on 12 November 2026. The same numbers can fit differently depending on the frame shape and nose pads, so an optician is the best person to check the fit, especially for strong or varifocal prescriptions. eyetest.co.uk may earn a commission if you buy through these links.
What the numbers on your glasses mean
Frames with a lens width of about 50mm or less are often called small, 51 to 54mm medium, and 55mm or more large. The bridge matters most for comfort, as it decides how the frame sits on your nose. Some frames also show a fourth number for lens height.
| Number | What it measures | Typical range |
|---|---|---|
| Lens width | The width of one lens at its widest point | About 40 to 60mm |
| Bridge | The gap between the lenses, where the frame sits on your nose | About 14 to 24mm |
| Arm length | The length of each arm, from the hinge to the tip | About 135 to 150mm |
