How to Measure Your Pupillary Distance (PD)

Pupillary distance (PD) measures the distance between the centers of your pupils and it’s usually measured in millimeters. It’s used to help center a prescription lens accurately in your frames so you can see clearly and should be as accurate as possible. The average adult’s PD is between 54-74 mm; childrens’ are between 43-58 mm. Your optician will usually measure your PD before ordering glasses, but if it’s not on your prescription, don’t worry, we have you covered. All you need is a ruler with millimeter measurements and a mirror or a friend. 

To make things even more simple, you can download this special PD ruler here. (Do not scale the image before printing.)

How to Measure Your PD?

  1. Stand 8 in. away from a mirror or a friend and hold a ruler against your brow.
  2. Close your right eye then align the ruler’s 0 mm with the center of your left pupil.
  3. Look straight then close your left eye and open your right eye.
  4. The mm line that lines up to the center of your right pupil is your PD.
1.  Mirror or Friend – Stand 8 inches (20 cm) away from a mirror or a friend. Place & hold the PD ruler against your brow. Keep your face straight.

2. Align to Zero – First, close your right eye and align the ruler’s zero to the center of your left pupil.

3. Open Right, Close Left – Next, open your right eye and close your left eye.

4. Your PD – Look straight ahead and read the millimeter line that matches up with the center of your right pupil. This number represents your single PD in millimeters.

Measuring Tips

Measure your PD 3-4 times to ensure it’s accurate and consistent.

  • Average Range of Adult PD: 54-74 mm
  • Average Range of Child PD: 43-58 mm

If a friend is measuring your PD, keep both eyes open and have your friend put the zero on the millimeter ruler over the center of one pupil, then measure the distance to the center of the other pupil.

  • Have them crouch/sit while you stand so they are out of your field of vision.
  • Keep your eyes as still as possible.
  • Look above his/her head at something approximately 10-20 ft. away.
  • Do not look at the person measuring!

Why is PD important?

All prescription lenses has an “optical center,” which is determined by pupillary distance. Pupillary distance is used to determine where you look through the lens of your glasses and should be as accurate as possible. DO NOT GUESS IT! If it’s wrong, it will be like buying the wrong size shoes. It will be uncomfortable and will not fit right.

Single vs Dual PD

SINGLE PD (or binocular PD) is the pupillary distance between the center of one pupil to the other, which can be a distance PD or near PD. Distance PD can be used to order any type of prescription glasses except reading glasses.

DUAL PD (or monocular PD) consists of two numbers and is the distance between the centers of each pupil to the bridge of the nose. Dual PD is usually written in the following notation: 32/30. The first number is always the right eye (OD) measurement, and the second number is the left eye (OS).

There's an app for that!

While there are several apps that are out there to measure PD and Seg Height, the one that has been most recommended to us by our customers is the EyeMeasure App for iPhones and iPads. If you choose to try the app, please, as usual, take the measurement at least 3-5 times to get a consistent result. You can download it from the Apple App Store here. Please note, we have nothing to do with the development of the app, and we cannot guarantee its accuracy.

Wearing Progressing Lenses?

For the perfectly smooth progressive experience, there’s another important measurement that will be needed to fill your prescription. This is called the Segment Height, or Seg Height. Read here for more.

Have all your measurements? Yay!

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