WORN Camera

Measure your wrist with your camera

Hold your wrist up with a card beside it, or beside your face. The camera finds your hand, measures the top of your wrist, and then draws any watch on it to scale, live, so you can see where its lugs land. It all happens in this browser: the pictures never leave your device.

Early access

WORN Camera is open to early access members

WORN Camera measures your wrist against a card or your own eye, in this browser, then draws any watch on it to scale, live. Enter your early access code to use it.

Ask for an access codeUse the free size calculator

Paid plans are on the way. Until then, WORN Camera is for people with a code.

How it measures

  1. It finds your hand. Google's MediaPipe hand model, running in this page, marks 21 points on your hand. From the wrist and the knuckles it knows where your wrist is and which way it runs.
  2. It needs a ruler. A camera sees pixels, not millimetres. A card in the ID-1 size (bank, ID and loyalty cards) is 85.60 mm long, so marking its two ends gives the scale exactly. Without a card, it uses your eye: the iris is roughly 11.7 mm across in most adults, give or take 0.5 mm, a figure Google's researchers use to judge distance from a single camera. That spread of about 4% is why the card is the precise way.
  3. It measures the top of your wrist. The model suggests the two edges of your wrist and you check them. That width is what WORN reads a watch against: a watch overhangs when its lug-to-lug is wider than the flat top of your wrist.

The circumference it shows is that width times pi, the same relationship the size calculator uses the other way round, so the two always give the same verdict. It is an estimate of the tape-measure number: if you want that exactly, wrap a strip of paper around your wrist.

For the best measurement

  • Hold the card (or your face) the same distance from the camera as your wrist: something nearer the camera looks bigger.
  • Show the back of your hand, flat on to the camera, in good, even light.
  • Move the marks with care: the magnifier shows the edge. One pixel is a fraction of a millimetre.

Your pictures stay with you

The camera's picture goes to the models running in your browser and nowhere else. WORN's servers never see it. The first time, the page downloads the hand model from Google's model storage (about 8 MB, and 4 MB more for the eye model), and the runtime that runs them from this site. Your measurement is kept in this browser only, so the size calculator and WORN Fit can use it.

For developers: Measure with WORN

Any site can ask a shopper for their wrist. With WORN Fit's loader on the page, WORNFit.measure() opens WORN Camera in a small window. The shopper measures, sees exactly which site asked, and chooses to share; your page gets the numbers and nothing else.

// on your page, from a click
const wrist = await WORNFit.measure();
// { type: "worn:wrist", wristMm: 168, flatTopMm: 53.5, method: "card" }, or null if they closed it

Without the loader, open https://worn.club/measure?return_to=followed by your page's origin, and listen for a message event from https://worn.club whose data has type: "worn:wrist".