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What is Pupillary Distance (PD)?

Pupillary distance (PD) is the measurement (in millimeters) of the distance between the pupils of your eyes.

Why is my PD measurement needed?

Pupillary distance is an important measurement used to determine the proper lens shape and alignment of your prescription correction to your line of vision. Without an accurate PD measurement, correcting vision can be difficult since lenses need to be aligned over the center of your pupil for proper clarity.

Where is my PD measurement on my prescription?

Your PD measurement is typically written beneath the prescription, as in the example below:

OD -3.75 -0.50 89
OS -5.25 -1.00 94

How do I read my PD measurement on my prescription?

Generally, adults have a PD within the range of 54-68 mm, while children have a PD within the range of 41-55 mm. Pupil distance can be measured in two ways. The first is called binocular, which is a pupil-to-pupil measurement, this type of measurement will be between 41-80 mm. The other type of measurement is called monocular, which is a per-eye measurement from the pupil to the middle of the face, this type of measurement will be between 20-40 mm. Monocular measurements are most often used when the face is not perfectly symmetrical, meaning one eye is closer or farther from the middle of the face than the other.

PD can be written on your prescription in a couple different ways. Below is a chart with some of the most common ways PD is written, along with how to enter the measurement when creating and purchasing glasses from our site.

PD looks like: PD measurement is: For glasses
that are:
Enter on
Rx page as:
P.D.: 62 Binocular PD measurement for both eyes (OU) Single-Vision
P.D.: 30.5 / 30 Monocular PD for both eyes. The left number is the left eye (OS) and the right number is the right eye (OD) Single-Vision
Reading Distance
63 66
Near/Reading and Far/Distance Binocular PD measurements for both eyes (OU). Progressive / Bi-focal

What if my PD isn't on my prescription?

PD is typically measured by your eye doctor during your eye exam. If your eyecare provider does not measure your PD during your eye exam, or if the PD is missing from your prescription, you can request a PD measurement. Some eyecare providers may charge an extra fee for a PD measurement, but many will include it as part of the eye exam. If your prescription does not have your PD measurement on it then you can measure your PD yourself by reading the "How do I measure my own PD" section.

How do I measure my own PD?

Follow the instructions below to measure your own PD at home.

Download your
FREE PD RULER (Adobe Reader required.)

Step 1. Download the PD Ruler above, or use a ruler that has millimeter measurements. You can also use a ruler with centimeter measurements and simply multiply the result by 10 to get your millimeter measurement. Or you can also use any straight object such as a book, magazine, piece of cardstock, etc. to mark the location of your pupils, then simply measure the distance between your marks.
Step 2. Stand about 8 inches (20 cm) away from a well lit mirror with your face parallel and square to the mirror. Hold the ruler just below your eyes, keeping it exactly horizontal.
Step 3. Close your left eye and align the ruler's zero (0) measurement to the center of your right pupil.
Step 4. Without moving your head or the ruler, open your left eye and close your right eye. Read the millimeter line that lines up with the center of your left pupil. This is your PD measurement.*
Step 5. Repeat these steps at least 3 to 5 times to get an accurate and consistent measurement. Make sure your head and the ruler do not move after lining up the zero (0) measurement with your right pupil until you note your measurement. Ask a friend to help if you are having trouble.

*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.

Still have questions? Call us at 1-888-248-5367 to speak to one of our trained Customer Service Representatives.