Glasses size guide: what the numbers mean
Most glasses carry three measurements inside one temple arm. Read them from a pair that already fits, and they give you the best starting point for finding another frame with similar proportions.
What do the three numbers on glasses mean?
1. Lens width
The first number is the horizontal width of one lens at its widest point. It is sometimes called eye size. A difference of a few millimetres changes both the overall proportions of the frame and how large the lenses look.
2. Bridge width
The second number describes the distance between the lenses at the bridge. It is an important starting point for how the frame sits on your nose, although bridge shape and nose-pad design mean two frames with the same number can still feel different.
3. Temple length
The final number is the length of the arm from the hinge towards the ear tip. Common adult lengths include 135, 140 and 145 mm. Arms can be adjusted, so an exact temple match is usually less critical than getting the front right.
Where can I find my glasses size?
Look along the inside of either arm. The size is often printed after the model or colour code and may use a square, dash or spaces as separators: 52□18 145, 52-18-145 and 52 18 145 normally describe the same three measurements.
If the print has worn away, measure the lens and bridge straight across with a millimetre ruler. Do not use your prescription or pupillary distance: those are different measurements.
Will the same numbers guarantee the same fit?
No. They are a strong way to narrow the catalogue, but they do not describe the entire frame. Total width, hinge position, bridge shape, material and how much the arms flex all affect comfort. Treat the printed size as a shortlist, then compare total frame width where the retailer publishes it.
Small, medium and large labels are not consistent between brands. Millimetres are the more useful comparison.
How SpecSearcher finds a similar fit
Enter the numbers from your current pair into the Fit section. SpecSearcher searches current listings from eyewear retailers serving UK shoppers and starts with a practical window around your pair: lens width within 2 mm, bridge width within 1 mm and temple length within 5 mm. You can tighten or widen any range.
Results are ordered by closeness to your pair. Product photos are also drawn on the same physical scale, so a narrow frame looks narrower than a wide one, and matching models sold by several shops are grouped for price comparison.
- Find the three numbers inside a pair that fits.
- Enter lens, bridge and temple measurements under Fit.
- Refine by total width, lens height, shape, colour, material or price.
- Open a frame to compare sizes, colourways and retailers.
Updated 30 August 2026 · Back to frame search