What are the numbers on the bridge of my glasses?
The numbers are your frame's size measurements, printed in millimeters: lens width first, then bridge width, then temple length, usually separated by spaces, dashes or a small square. They describe how the frame fits rather than the model or brand, and they're a reliable starting point when shopping for a similar pair.
If you have ever taken off your glasses, tilted them toward the light and squinted at a string of tiny digits, you have already done half the work of understanding frame sizing. Those markings are eyeglass measurements. One thing worth clearing up first: the sizing numbers are most commonly printed on the inside of one arm (the temple), not necessarily on the bridge itself, though some frames place markings elsewhere. Wherever you find them, the sequence means the same thing.
[1]The three numbers, in order
Frames usually carry up to three numbers, in the same order and expressed in millimeters. The first is the lens width, sometimes called the eye size, which measures the width of one clear lens only, not including the frame around it. The second is the bridge width, which is the shortest span between the two lenses. The third is the temple length, measured from the screw where the arm attaches to the frame all the way to the tip that rests behind your ear. A small square symbol often separates the first two numbers, and other letters or digits nearby may refer to the model, colour or brand rather than the size.
[1]| Measurement | What it measures | Typical range |
|---|---|---|
| Lens width | Width of one lens, excluding the frame | 40–60 mm |
| Bridge width | Shortest distance between the two lenses | 14–24 mm |
| Temple length | Hinge to tip of the arm | 120–150 mm |
Why the bridge number matters for fit
The bridge width is the one people most often misread, because it is not simply the size of the visible bridge piece. It is the gap between the lenses. A smaller bridge width suits a narrower nose, while a larger one suits a wider nose. If your glasses slide down, the bridge number is one thing to check. Temple length matters too: the arms should extend behind your ears without protruding far past them, and common lengths such as 135, 140, 145 and 150 often end in a zero or five.
[1]A worked example
Suppose the inside of your arm reads 52 18 140. That means each lens is 52 mm wide, the lenses sit 18 mm apart, and each arm is 140 mm long. If those glasses fit well, that trio is a solid starting point for your next pair. When comparing frames, keep the full model and colour code alongside these numbers, because a brand or product family can include several different frames, and missing size information is a reason to check with the retailer before buying. The same numbers can also help you confirm you are looking at the exact same product, not a similarly named one, when comparing prices between retailers.
[1][2]If the numbers are worn away
Older frames sometimes lose their markings to wear. You can measure them yourself with a millimeter ruler: measure one lens horizontally at its widest point, measure the gap between the lenses at their nearest points, and measure the temple in two parts, from the hinge to where it begins to curve and from the curve to the tip, then add those together. An optician can also take these measurements for you, which is worthwhile if you are switching to a very different frame style.
[1]One caution: measurements are guidelines, not guarantees. Two frames in the same size category can still feel different depending on frame thickness and materials, and factors like pupillary distance affect how your lenses are positioned even though they do not change the frame size. Comfort and fit still need to be judged on your own face. Your practical next step: find the three numbers on your current pair, write them down with the full model code, and use that combination as your reference point the next time you compare frames or prices.
[1]Sources and dates
- https://www.warbyparker.com/learn/eyeglasses-measurements · accessed 2026-10-18
- https://eyewearcompared.com/ · accessed 2026-10-18