Glasses measurements: what do 52, 18 and 145 mean?

Found a frame you love but unsure which size to choose? Start with the numbers inside the temple: 52 □ 18 145 means a 52 mm lens width, an 18 mm bridge and 145 mm temples. These measurements are a starting point, not a guarantee of fit: frame shape, overall width and nose support also matter.

Where to find the numbers

Measurements are usually printed inside a temple or on the bridge, near the model and colour codes. They are given in millimetres. The small square generally separates lens width and bridge width; it is not a prescription value.

52 is the width of one lens, not the whole frame

Lens width is the horizontal width of the lens without the frame rim. In this example it is 52 mm. A 54 mm lens is wider, but different models cannot be compared by lens width alone: bridge width, rim thickness and hinge design also affect overall frame width.

18 is the bridge; 145 is the temple length

Bridge width is the distance between the lenses: 18 mm here. Bridge shape and nose pads influence how the frame rests on your nose. Temple length, here 145 mm, runs along the temple from its attachment at the front to the tip. It does not measure the width of your face.

Check the size before ordering

Compare all three numbers with a pair you already wear comfortably. Check overall frame width when it is provided. Adding twice the lens width to the bridge width does not necessarily include the entire frame structure and cannot replace an external width measurement. A different shape can feel different even when the numbers are similar.

What a comfortable fit feels like

During a fitting, check for pressure at the temples, repeated slipping and contact with your cheeks when you smile. The temples should sit behind the ears without uncomfortable pressure. For prescription glasses, fit must also be considered alongside lens requirements and centration: frame size is not your pupillary distance.

From measurements to your next frame

Read the size guide for more detail. Use the measurements on the product page as a comparison, not as a promise that every frame with the same numbers will fit identically. If you are unsure, an optician’s fitting is more informative than choosing an S, M or L label alone.