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Measuring Pupillary Distance (PD)

Pupillary distance (PD) is required when ordering prescription eyeglasses online. If a PD isn’t listed on the prescription, download our helpful pupillary distance ruler PDF and follow the directions below.

PD Measurement Ruler

What is Pupillary Distance (PD)?

Pupillary distance (PD) is the distance between the centers of the pupils of your eyes. Your PD is needed to correctly center the lenses within the frame so your prescription is to your line of vision. To order glasses online, you’ll need to put your pupillary distance in the “PD” box when entering your prescription.

How to Measure Pupillary Distance

Your pupillary distance is often measured by your doctor during an eye exam, but is not always listed on the prescription. However, you can measure your PD online with a few simple steps as long as you have a mirror and a ruler with millimeter measurements. Our video will help guide you through the process.


  1. Hold a ruler against your brow and look straight ahead into a mirror.
  2. Align the ruler's 0 mm mark with the center of the left pupil.
  3. The millimeter line that aligns with the center of the right pupil is the PD.

Note: These instructions are for getting your Distance PD measurement. If you require prescription bifocal glasses then you will also need your Near PD, which is calculated by subtracting 3mm from this Distance PD measurement.

Frequently Asked Questions

Q: Can I measure my PD without a ruler?
A: If you don’t have a ruler with millimeter markings, download our PDF pupillary distance ruler.

Q: What is the average PD?
A: An average pupillary distance for adults is within 54-68 mm, while children have an average PD within 41-55mm.

Q: Where is my PD on my prescription?
A: Your pupillary distance should be listed under the “PD” section in your prescription which can be separate from where your prescription is written.

Q: What if my PD is not exact?
A: Your PD measurement should be as accurate as possible. If your prescription lenses are not centered to your line of vision, it can cause eye strain, dizziness, headaches, and blurred vision.

Q: What’s the difference between single and dual PD?
A: The distance between one pupil to the other pupil is the ‘single’ pupillary distance. This can be a distance PD or a near PD. The distance PD can be used for any prescription glasses except for reading glasses. The distance between each pupil to the center of the nose is the ‘dual’ or monocular pupillary distance. The first number is the measurement for the right eye (OD) and the second number is the left eye measurement (OS).

Q: Will my pupillary distance change?
A: For children or young adults that are still growing, their pupillary distance will change. Once a person becomes a fully grown adult, their PD will most likely stay the same.

If you have any other questions, our Customer Service Team will be happy to help.

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