Measure Your PD Online

Get your pupillary distance — the millimeter measurement lens labs need to position prescription lenses correctly — in under a minute. All you need is a standard card to hold against your forehead as a size reference. Detection runs entirely in your browser, so no photos are uploaded.

How to measure your PD

  1. Hold a card against your forehead. Any standard card works — a debit card, ID card, or credit card. We use it as a known-size reference so the AI can calculate real-world distances from your camera image.
  2. Start the camera. Tap "Start". The detector runs in your browser — your photo never leaves your device.
  3. Look straight at the lens. Hold the phone at arm's length, level with your eyes. Keep your gaze on the camera and don't tilt your head.
  4. Hold steady for the scan. Stay still while the AI locates your pupils relative to the card. Takes about two seconds.
  5. Save your PD. Read your result in millimeters (a typical PD is 54–74 mm). Save it for checkout, or measure again to double-check.

Frequently asked questions

What is pupillary distance (PD)?
Pupillary distance is the distance in millimeters between the centers of your two pupils. Lens labs use it to align the optical center of each lens with your pupils, so your prescription works as intended. A PD that is off by even a few millimeters can cause eye strain or blurred vision.
Why do I need to know my PD to order glasses online?
When you buy prescription glasses, the lab needs your PD to grind and position the lenses correctly. Optical shops measure it during fitting; for online orders, you provide it yourself. You can ask your optometrist, measure manually with a ruler and a mirror, or use a tool like this one.
How accurate is the AI PD measurement?
Our tool uses MediaPipe facial landmarks and a known-size reference card (your debit/credit card) to convert pixel distances to real-world millimeters. In good lighting with the card held flat against your forehead, results are typically within 1–2 mm of an optometrist's measurement — well within the tolerance most lens labs accept.
What's a typical PD range?
Adult PD ranges from about 54 mm to 74 mm; most people fall between 58 mm and 68 mm. Children typically have smaller PDs (43–58 mm). If your result is outside the adult range, take a second measurement to confirm.
What if my two eyes have different PDs?
A few percent of people have a slightly asymmetric PD — say, 31 mm left and 33 mm right. If you suspect this, ask your optometrist for a "monocular" PD measurement, which reports each eye independently. Most online retailers (including rimloo) accept both single-number and two-number PDs.
Is my photo stored or sent anywhere?
No. PD detection runs entirely in your browser using on-device machine learning. No image data is uploaded, stored, or shared — only the final PD number is saved (to your browser, for the checkout form).