Eyewear is not sized S, M, L. It is sized in millimetres, and three of them decide whether a frame will sit on your face or slide off it. All three can be measured from a single photograph — the try-on does it automatically, using your iris as the ruler.
Temple to temple, across the widest part of your face. This is the one that decides everything. A front should be about as wide as your face — a couple of millimetres proud on each side is correct, because the rims then clear your cheekbones and the arms fall straight back to your ears. Much wider and the frame walks down your nose. Narrower and it presses, and leaves marks.
Most adults: 128–150 mm
Centre of one pupil to the centre of the other, usually written PD. Every frame has one too — its lens width plus its bridge, which is the distance between the geometric centres of the two lenses. When yours is close to the frame’s, your eyes sit in the middle of the lenses. When it is far off, they sit inboard or outboard of centre: on a dark lens that is invisible, on a clear or prescription lens it is not.
Most adults: 54–74 mm · average 63
How much vertical room there is between your pupil and the top of your cheek. A lens taller than that room rests on the cheek, lifts every time you smile, and marks the skin. Deep lenses need a long face; a shorter face wants a shallower frame, whatever the fashion is doing.
Measured from: pupil to the base of the nose
These are not catalogue figures. Each one is measured from the frame’s own 3D geometry — the same file the studio above renders — which is why they carry a decimal. Read the first three the way an optician writes them: eye □ bridge, then lens height.
| Frame | Eye | Bridge | Lens height | Front width | Temple | Suits a face of |
|---|---|---|---|---|---|---|
| MATRIARCA | 51.7 | 24.9 | 34.5 | 142.5 | 139.8 | 134–144 mm |
| PATRIARCA | 51.7 | 24.9 | 34.5 | 142.6 | 143.4 | 134–144 mm |
| ARCA I | 54.6 | 20.5 | 39.6 | 142.9 | 150.5 | 134–144 mm |
| MONARCA | 52.3 | 19.2 | 42.3 | 145.3 | 142.2 | 137–147 mm |
| DOXA | 46.3 | 31.7 | 40.8 | 148 | 159.2 | 140–150 mm |
| AVAD | 52.7 | 20.9 | 42.8 | 149.3 | 168.7 | 141–151 mm |
| LOGOS | 50.8 | 24.6 | 41 | 150.3 | 158.5 | 142–152 mm |
| ARCA II | 54.2 | 20.3 | 39.4 | 151 | 147.1 | 143–153 mm |
| AHAVA | 51.6 | 18.7 | 38 | 151.6 | 150 | 143–153 mm |
| LEGATE | 56.3 | 26.8 | 48.4 | 164.4 | 168.6 | 156–166 mm |
Our narrowest front is MATRIARCA at 142.5 mm and the widest is LEGATE at 164.4 mm. This is a house that makes a substantial frame; if your face measures under 130 mm across, start at the top of that table.
A photograph has no scale of its own. A face across the room and a face up close are the same face, and nothing in the pixels says which. The usual fix is to hold a bank card against your cheek: every card on earth is 85.60 mm wide by standard, so the card fixes the scale.
You already carry a better ruler. The coloured part of the eye — the iris, measured left edge to right edge — is 11.7 mm across in almost everyone, give or take half a millimetre. It does not track your height, your age past childhood, or anything else. Horizontally specifically, because your eyelids cover the top and bottom of the iris but never its sides. Find the iris in the photograph, and every other distance in it converts to millimetres.
That half-millimetre spread is about 4%, and it is a floor: it is why the measurement is shown with a ± rather than as a single figure. Turning your head is the other source of error, so the tool refuses to answer past 18 degrees of turn instead of quietly giving you a number that is wrong.
This is not our idea — it is an established clinical method. A 2023 study in Scientific Reports built an automated system that scales facial measurements in photographs to real millimetres using exactly this reference, the horizontal visible iris diameter. Across 94 subjects it came within 2.9% on horizontal measurements and 4.3% on vertical ones against measurements taken by hand on the actual face. Their conclusion was that the iris is “a reliable scale to calibrate the magnification of the images”. Pirayesh et al., Scientific Reports, 2023 ↗
And heads genuinely differ. The iris is the steady part; almost nothing else about a face is. Adult head breadth varies by well over a centimetre between people of the same height, which is precisely why a frame sized from an average fits badly on most faces and why we measure yours instead of assuming it. The iris reference itself carries a small population variation too — the literature places the mean between about 11.7 mm and 12.2 mm depending on the group studied — and that is the honest floor under the ± we show. It is a measurement, not a certainty, and we would rather say so than quote you a single confident number that is quietly wrong.