How to Measure Your Face for Glasses: Five Minutes, a Ruler and Three Numbers

Why this matters more here than with ordinary glasses

Buy regular frames in a shop and an optician heats the arms, bends them to your head, adjusts the pads and hands them back fitting. Almost none of that is available in this category. The battery and speakers run the length of each temple, so the arms are thick and, on most models, not bendable. The frame comes in one size - Meta sells a Large Wayfarer and nobody sells a Small. And the vast majority of these are bought online, unopened, on the strength of a photo.

Which means the fit decision happens before you pay, from numbers. Fortunately there are only three of them, and the numbered method above gets you all three in about five minutes.

Reading the code inside your temple

Take any pair of glasses that currently fits you and look inside one arm, usually near the hinge. You will find something like 52 □ 20 145, occasionally written with a dash or no separator at all.

• First number - lens width in millimeters. The horizontal width of one lens. 48-51 is a small to average frame; 52-55 is average to large. The Ray-Ban Meta Wayfarer Standard is 50 mm, the Large is 53 mm, the Oakley Meta HSTN is 49 mm, the Lucyd Millennia petite front is 51 mm.
• Second number - bridge width. The gap between the lenses, across your nose. The Wayfarer is 22 mm, the HSTN 23 mm, the Millennia 20 mm. A smaller bridge on a wide nose pinches; a larger one on a narrow nose slides.
• Third number - temple length. The arm, hinge to tip. HSTN 145 mm, Wayfarer Standard 150 mm, Wayfarer Large 155 mm. This is the number people forget and it is the most common cause of a frame that hurts behind the ears.

Matching your numbers to what is actually sold

What about pupillary distance?

If you are ordering prescription lenses, the retailer will ask for your PD - the distance between your pupils in millimeters - and you should get it from your prescription or your optometrist rather than measuring it yourself. The at-home mirror-and-ruler method is fine for frame width; it is not accurate enough for lens centration, and an off-center prescription lens causes eye strain in exactly the way this whole page is trying to avoid. The pairs that take a prescription, and the ranges each one accepts, are on the prescription guide - Meta's own-brand frames stop at -6.00 to +2.25, while the Even Realities G2 runs -12.00 to +12.00.

Three frames your numbers will probably land on

Ray-Ban Meta Wayfarer Large (Gen 2) if your face measures wide: 137 mm hinge to hinge, 53 mm lenses, 44 mm lens height, 155 mm temples, with identical electronics to the Standard. It is the only Gen 2 style sold in a Large. Ray-Ban Meta Skyler (Gen 2) if the frame slides: one size, butterfly shape, with a choice of Standard or High bridge and seven frame colors. Meta Adventurer if you are between sizes or expect to need adjustment: Standard and Large, adjustable temple tips and over-extension hinges, the same 12 MP / 3K camera as a Gen 2 for $80 less at launch - with a narrower prescription range as the trade.

Two mistakes that cost people a return

Buying by photo. Frames photograph larger or smaller depending on the model wearing them. Lens height in particular - 44 mm on a Wayfarer Large - is invisible in a product shot and is what decides whether the rim sits on your cheek.

Assuming the arms can be bent. On most smart glasses they cannot: there is a battery in there. If your measurements are borderline, pay the premium for a frame with adjustable temple tips or interchangeable nose pads, and budget a short optician appointment. That advice applies double if you have a wide head, which is covered in detail on the fit guide for big heads and wide faces, or a narrow one, which is on best smart glasses for small faces.