How the Pupillary Distance app works on iPhone

The camera you already have

Every Face ID iPhone ships with a TrueDepth front camera. Apple uses it to unlock your phone and to map faces for AR. We use that same camera to locate the center of each pupil in three dimensions and measure the distance between them — the same measurement an optician takes with a pupillometer.

Your pupillary distance is usually between about 54 mm and 74 mm. The app reports your far PD (for distance lenses), your near PD (for reading), and your left and right monocular PD measured from the bridge of your nose. Because the measurement is taken in millimeters from depth data, it's accurate enough to order glasses online.

Tips for an accurate reading

• Hold the iPhone at about arm's length, roughly level with your eyes.
• Look straight into the front camera and keep your head still while it measures.
• Measure in good, even lighting so your pupils are easy to detect.
• Take off your glasses, and move tinted or reflective lenses out of the way.
• Run the measurement a couple of times — consistent results mean a clean reading.

When the app is the right tool

For ordering everyday eyeglasses or sunglasses online, a TrueDepth PD measurement is fast, private, and always in your pocket — and the app can also suggest frame styles for your face shape. For high prescriptions, progressive lenses, or specialized eyewear, treat the app as a convenient starting point and confirm your PD with an optician. For frame styling, see how the frame recommendations work.