How to measure your Pupillary Distance

What is PD?

Pupillary Distance (PD) is the measurement in millimetres of the distance between the center of each of your pupils. This is also called binocular PD. It is used to ensure that your lenses are positioned correctly to give you the best comfort and clear vision.

Why does PD matter?
In order to make your eyeglasses custom to your face, we need to know the distance between your pupils so the optical center of the eyeglass lens, which holds the clearest vision, sits directly in front of your pupil.

Also, when ordering glasses online, your PD value is required to place an order for a new pair of prescription glasses or prescription sunglasses.

How to measure your PD

You are able to measure your own PD. This comes in handy when you want to order your prescription glasses online and already have your prescription but don’t know your PD, you can measure your own PD using a ruler and a mirror.

We do recommend getting your PD measured in-store by our optometrist or optical dispenser. This can be done when you are being fitted for your new glasses using a pupilometer or PD meter.




  1. You will need a ruler and a mirror.
  2. At a distance of about 20cm away, look front on into the mirror.
  3. Hold the ruler just above your eyes and place it against your brows, making sure you keep your face front on to the mirror.
  4. Close your right eye and align the ruler from zero to the centre of your left pupil.
  5. Without moving your head or the ruler, open your right eye and close your left eye. Read the millimetre line that lines up with the centre of your right pupil. This number represents your PD in millimetres.

  6. Repeat the entire process a few times to get a consistent measurement.



What you just measured is your Distance PD. If you need your PD measurement for prescription reading glasses then you will need to know your Near PD which is calculated as 2mm less than your Distance PD.

For example:

Distance PD: 62mm, Near PD: 62 - 2= 60mm



Single PD vs. Dual PD

Single PD (also called binocular PD) is the total measurement between the pupils, as explained above.

Not all eyes are equally proportioned and one pupil could be a couple of millimetres further away from the nose bridge than the other. Dual PD (called monocular PD) is the two measurements between the center of each pupil to the bridge of your nose. It is usually written with Right Eye first and Left Eye second: 30/31.

It is important for your PD measurement to be as accurate as possible so your new glasses are made correctly and for you to be able to see out of them clearly.

If you’re unsure about your PD measurement, visit an Oscar Wylee store near you and our friendly team can assist you.

Useful Tips

• If you are unable to measure yourself, have someone help you!
• Try to keep your face still and look straight ahead
• If you’re still unsure or want an accurate reading of your PD or Dual PD, visit an Oscar Wylee store near you