Reading frame sizes

Every pair of glasses ever made carries three numbers on the inside of the temple arm. They are the only reliable way to tell whether a frame will fit you, and almost nobody knows how to read them.

The three numbers

• 54: the lens width, sometimes called the eye size. The horizontal width of one lens in millimetres. Most adult frames sit between 44 and 58. This is the number that changes most between frames and the one worth learning for yourself.
• 17: the bridge, the gap between the two lenses, across the top of your nose. Usually 14 to 24. A bridge that is too wide lets the frame slide; too narrow and it perches and pinches.
• 145: the temple length, the arm, from hinge to ear tip. Almost always 135, 140, 145 or 150, and the one you can most often get away with ignoring, because arms can be adjusted.

The little square between the first two numbers is not a typo or a missing character. It is the symbol for the boxing system, the measuring standard the whole industry has used since the 1970s.

The number nobody prints

What actually decides whether a frame fits is its total width: lens, bridge, lens, plus the rim on either side. For the Quarry that comes to about 136mm. Compare that against the width of your own face at the cheekbones: a frame should finish at that width, or a whisker beyond it.

Too narrow and it grips your temples and leaves marks. Too wide and it slides down your nose all day, whatever you do to the arms. Roughly ±4mm is comfortable; beyond about 9mm out you are wearing the wrong size frame.

This site shows total width on every frame card and works out your own face width from a photo, which is the whole reason for the measuring page.

Lens height, the forgotten one

Rarely printed, and it matters more than people expect. Lens height (the B measurement) decides whether a frame reads as a statement or disappears, and if you wear varifocals it is not optional: most varifocal lenses need at least 28–30mm of height to fit the reading section in at all. The Quarry has 37mm.

Working out your own size without a tape measure

1. Find a pair of glasses or sunglasses you already own and like the fit of.
2. Look inside the left arm for the three numbers.
3. Shop within about 2mm of that lens width and bridge, and you will be right far more often than not.

If you have never owned a pair, measure your face with the camera. It returns a suggested total width and lens width in real millimetres, alongside your PD.

Why this site is built on these numbers

Every frame here is drawn from its measurements rather than photographed. The shape family gives the outline, the millimetres give the proportions, and the same geometry produces both the catalogue picture and the 3D model that lands on your face in the try-on. That is why the two always agree, and why a 54mm frame genuinely looks wider on you than a 48mm one.

How the try-on works →