Eyewear measurements explained: lens, bridge and temple

The three numbers that decide fit

Almost every frame carries three numbers inside the temple, for example 52-18-145. The first is the lens width in millimetres, the second is the bridge, the distance between the two lenses, and the third is the temple length from hinge to tip. Reading them is the only reliable way to buy eyewear online, because a model name tells you very little: the same reference often exists in two or three different sizes.

Working out total width

Approximate frontal width equals twice the lens width, plus the bridge, plus roughly six millimetres for rims and hinges. A 52-18 therefore measures about 128 millimetres. Compare that with the distance between your temples, measured in a mirror with a soft tape. If the frame is four or five millimetres wider it will slide down; if it is narrower it will pinch and leave marks after a couple of hours.

The bridge matters more than people think

The bridge decides where the frame sits and how well the lenses stay centred on your pupils. Too wide and the glasses slip down your nose, pushing the optical axis upward; too narrow and the frame rides high, pressing on the sides of the septum. If you have a low nose bridge, look for smaller bridge measurements or adjustable nose pads, common on metal frames and Japanese constructions.

Temple length and hold

Standard temples measure 140, 145 or 150 millimetres. 145 is the most common size and works for most adults; 150 suits deeper heads or tied-back hair, while 140 helps if the temple presses behind your ear. A frame that rests only on your ears without stable contact on the nose almost always has temples that are too short, not lenses that are too wide.

Curvature and lens height

Two figures that are never printed on the temple matter just as much. Frontal curvature, expressed as base curve, decides how much the frame wraps around your face: a base-8 sports frame on a flat face leaves side gaps and lets light in. Lens height determines compatibility with progressive lenses: below thirty millimetres progressive corridors become uncomfortable to use.

Using measurements on FRAMEO

Every catalogue model page on FRAMEO lists lens width, bridge, temple, total width and, where available, lens height. Our face fit tool compares your own measurements with the frame and returns an indicative band, so you can filter the catalogue by size before you even look at price. When in doubt, compare the numbers with a pair you already wear well: it is the most honest reference you will find.