What is my PD?

(also called Pupillary Distance, Inter-Pupillary Distance or Pupil Distance) PD is the distance between the centre of one pupil to the centre of the other pupil. Prescription glasses are made so that the distance between the optical centres of the glasses' lenses, is the same as your PD. PD varies from person to person but once you are an adult, your PD does not change. Therefore, as an adult, if you have had it measured, then it will still be the same, even if your spectacle prescription has changed. Once you know your PD, you do not need to measure it every time you buy prescription glasses. PD is measured either during the eye test or when prescription glasses are ordered. Obviously we cannot measure your PD over the internet, so it is best to make sure your PD is included in your glasses prescription.

The Diagram below represents a PD of 62mm.

             If your prescription does not contain your PD:

  • Ask to have it measured at an optical shop – some may charge a fee.
  • Contact an optical shop where you have previously purchased prescription glasses. Your PD has been measured if you have ever had prescription glasses made up. Your previous optometrist may have a record of your PD.
  • Alternatively, try measuring your own Pupillary Distance as explained below. (Note: Measuring your own PD may not be as accurate as having a trained person do it. If your head or the ruler moves during the measurement then the reading will be inaccurate)

Measure Your PD:

This technique uses a second person to measure your Pupillary Distance (PD).

1. Both of you should be sitting down approximately 45cm apart. The person having their PD measured keeps both eyes open. When your friend is taking the measurement, they must keep one eye closed.

2. The ruler is held against the forehead as shown above. The person having the PD measured looks into the open eye of the person taking the measurement. The “0” is lined up with the centre of one pupil. Record the number lining up with the centre of the other pupil in millimetres.

If you have problem for this technique you can just take a simple picture like the one below with a dollar-bill against the side of your eye.Then we will be able to measure your P.D. accurately.

Please note that when you measure your own PD by using these techniques you may not get the same result as an experienced professional. We recommend that you use the measurements taken by an optometrist or an optical dispenser whenever possible. This page is provided for information purposes only. We do not take responsibility for the accuracy of measurements taken by people referring to this information. Please note that professional optical dispensers and optometrists may use different techniques to measure your PD.