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pupillary distance.
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Pupillary distance (PD) is the distance in millimetres between the centres of your two pupils. It tells the lab where to place the optical centre of each lens so your prescription lines up with your eyes. PD is required to order prescription glasses online.

Hold a credit or ID card flat against your forehead in the same plane as your eyes, look straight at your webcam or take a front-facing selfie, then let the tool detect your pupils and the card's edges. Because the card is exactly 85.60 mm wide, it converts pixels to millimetres for an accurate measurement. You can also print our PD ruler and use a mirror.

Yes. You don't need an optician to measure PD. With a webcam or a single selfie and a standard plastic card for scale, you can measure your PD at home in under a minute, completely free and private.

PD isn't legally part of your glasses prescription in most places, so some opticians leave it off or charge a fee — partly because it makes buying glasses elsewhere harder. You're free to measure it yourself and take the number to any retailer.

For adults, average PD is roughly 63 mm — about 61 mm for women and 64 mm for men, with most adults falling between 54 and 74 mm. Children have smaller values. Our tool shows where your PD sits in this range.

Single (binocular) PD is the total distance between both pupils. Dual PD, also called monocular PD, is measured separately for each eye from the centre of the nose — for example 31.0 / 31.5. Dual PD is more precise and is often used for progressive lenses. This tool reports both.

For dedicated reading glasses, a near PD is useful because your eyes converge inward when focusing up close. Near PD is typically about 3 mm smaller than your distance PD. We calculate an estimated near PD automatically, but confirm it with an optician for strong reading prescriptions.

With good lighting, a steady head and careful card alignment, a webcam measurement is typically accurate to within about ±1–2 mm. Our camera mode captures multiple frames and shows a confidence range so you know how reliable your result is. It's a measurement aid, not a medical device.

No. All detection runs locally in your browser using on-device machine learning. Your photo or camera image never leaves your device and is not uploaded, saved, or sent to any server.

Most adults have a PD between 54 and 74 mm. Values a little outside that range can still be perfectly normal — PD simply reflects the natural spacing of your eyes.

Yes. Print our true-to-scale PD ruler, hold it against your brow in front of a mirror, and read the millimetre mark over each pupil. It works fully offline with no camera and no app.

A PD measurement is your pupillary distance — the distance in millimetres between the centres of your two pupils. It tells the optical lab where to place the centre of each lens, which is why online glasses retailers ask for it at checkout.

For glasses, a PD measurement positions each lens directly in front of your pupil so you look through the correct part of the lens. An accurate PD keeps vision comfortable; an off PD can cause eye strain or blur, especially in stronger prescriptions.

You can get your PD measurement in about a minute at home: hold a credit card to your forehead for scale, look into your webcam or take one photo, and this free tool converts the image to millimetres. No optician or app is required.

Print our true-to-scale ruler at 100%, hold it flat against your brow in front of a mirror, line up 0 mm over one pupil, and read the millimetre mark over the other. That number is your PD. See the printable PD ruler.

Online PD measurements — whether from a retailer like Zenni or a private tool like this one — are typically accurate to within about ±1–2 mm when you use good lighting and a card for scale. Take two readings to confirm, and check strong prescriptions with an optician.

PD usually isn't a legally required part of a glasses prescription, so some optometrists leave it off or treat it as part of in-store dispensing. You're free to measure it yourself — see why opticians won't give your PD.

A typical adult PD measurement is around 63 mm — roughly 61 mm for women and 64 mm for men — with most adults between 54 and 74 mm. Children have smaller values that grow with age.

An adult's PD is stable and changes very little once the face is fully grown, so a measurement from a year ago is usually still accurate. Children's PD increases as they grow, so re-measure a child every year or two.

If your PD is off by more than a couple of millimetres, the optical centres of your lenses sit away from your pupils, which can cause eye strain, headaches or blurred edges — more noticeably in stronger or progressive lenses. Re-measure and average a few readings to be safe.

An accurate PD measurement aligns each lens with your eye. For low prescriptions a small error is usually tolerable, but for high powers, prism or progressive lenses, precision matters — confirm the number with an optician for those.

Yes. Open this tool in your phone's browser and use the photo method: hold a credit card next to your eyes for scale and take a front-facing selfie. Everything is processed on your phone — no app to install and nothing is uploaded.

Yes. You can measure your pupillary distance online for free with your webcam or a single photo — a standard card provides the scale and the tool converts it to millimetres in your browser. It's a private alternative to a retailer's checkout PD tool.

You can measure your PD by yourself in three ways: a guided webcam capture, a selfie with a credit card for scale, or a printed true-to-scale ruler read in a mirror. Each takes about a minute and needs no second person and no optician.

Yes, a PD of 70 mm is within the normal adult range, which runs from about 54 to 74 mm. It's on the wider side but perfectly common, especially for men. Order your glasses with your exact number rather than rounding to an average.

A PD that's off by 1 mm is usually fine for standard single-vision glasses, and 2 mm is often still acceptable. Larger errors — or any error with strong, high-index or progressive lenses — can shift the lens's optical centre enough to cause eye strain, so measure twice and average your readings.

Yes. Stand about 20 cm from a mirror, hold a millimetre ruler flat against your brow, line up 0 mm over one pupil and read the mark over the other. Our printable PD ruler makes this easier, but any accurate mm ruler works.