What is Pupillary Distance (PD) and How to Measure It At Home?

Ever wonder what you’re supposed to put in the “PD” box when you’re entering your prescription online? Pupillary distance (PD) is the distance between the centers of the pupils of your eyes, and it’s used to determine the proper lens shape and alignment of your prescription to your line of vision.

Although your PD is often measured by your eye doctor during your exam, PD measurements are not always listed on your prescription—but, no worries, it’s easy enough to obtain using a ruler and a mirror. Download our PDF ruler and follow instructions to measure your own PD at home.

• Hold a ruler against your brow
• Align the ruler’s 0 mm mark with the center of the left pupil
• The millimeter line that aligns with the center of the right pupil is the PD

Adults generally have a PD within 54-68 mm, while children have a PD within 41-55 mm.