Stand 8 in. away from a mirror. Hold a ruler against your brow.
Close your right eye then align the ruler’s 0 mm with the center of your left pupil.
Look straight then close your left eye and open your right eye.
The mm line that lines up to the center of your right pupil …
Pupillary distance (PD) measures the space between the pupils of your eyes. Knowing this measurement is important to make sure your eyes match up with the optical center of your lenses. The average adult’s PD is between 54-74; kids' are between 43-54.