Pupillary Distance (PD)

Pupil distance (PD) also referred to as interpupillary distance, is the measurement in millimeters from the center of the pupil in the right eye, to the center of the pupil in the left.

This measurement is used to determine the point you look through the lens of your glasses’ optical center, so it is important to measure accurately.

If you do not have this info from your eye doctor, you can measure it yourself or ask a friend to help you.


  1. Stand 8 in. away from a mirror.
  2. Hold a ruler against your brow.
  3. Close your right eye and align the ruler’s 0 mm with the center of your left pupil.
  4. Look straight then close your left eye and open your right eye.
  5. The mm line that lines up to the center of your right pupil is your PD.

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