What the Numbers on Glasses Mean
The numbers on glasses, 52 18 140 for instance, are three sizes in millimetres: lens width, bridge width and temple length. One arm has them printed on its inner side, with a box sign sometimes placed between the first two.
- 52mm across each lens
- 18mm bridge between the lenses
- 140mm long temple (arm)
52 □ 18 · 140
Where to Find the Numbers on Your Glasses
Near the hinge, look at the inside of the left or the right arm. Some frames place the numbers on the bridge instead, or behind the nose pads. Usually the model and colour code appear as letters and numbers ahead of the sizes.
Lens Width
Lens width comes first: it measures one lens at its widest point. Most frames fall between 40 and 60 mm. Small means a width of up to 50 mm, 51 to 54 mm is medium and 55 mm or above is large (EyeBuyDirect).
Width of the Bridge (Bridge Size)
The gap between the two lenses, the part that rests on your nose, is the second number: the bridge width. Bridge sizes run from about 14 to 24 mm. On metal frames with nose pads, a bridge 2 to 3 mm off your current size can still usually be adjusted to fit (Clearly).
Temple Length
The third figure is the temple length, or arm length: the distance each arm covers from hinge to tip. You will often see lengths of 135, 140, 145 and 150 mm. Arms that are too short press behind your ears; ones that are too long let the glasses slip.
Other Measurements and Lens Height
The arm rarely shows the lens height, which means how tall the lens is at its tallest point. Most shops list it with each frame. Progressive lenses need it because the reading zone requires enough height. Some shops also show total frame width, measured from hinge to hinge.
What the Numbers Leave Out
Your PD is not shown on the arm. The bridge added to lens width gives the frame PD: 52 + 18 = 70 mm, the distance from one lens centre to the other, not between your pupils. Your own PD is still required to order lenses: measure it with your camera.
Frame Number Questions
What is the meaning of the box sign found between the numbers?
The box sign tells you the sizes follow the boxing system, where each lens is measured inside a rectangle.
Do sunglasses use the same numbers?
Yes. The same lens width, bridge and temple figures appear on sunglasses.
On glasses, what does 135 or 140 stand for?
The figure is the temple length: from hinge to tip the arm measures 135 or 140 mm.
Chart and finder for your glasses frame sizeMeasure your own PD