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How To Measure Pupillary Distance (PD)

What Is Pupillary Distance?

PUPILLARY DISTANCE (PD) measures the distance between the centers of your pupils. This measurement is used to determine where you look through the lens of your glasses and should be as accurate as possible.

The average adult’s PD is between 54-74 mm; kids’ are between 43-58 mm.

If you don’t have your PD from your eye doctor, you can measure it yourself with the help of a friend, or you can measure it yourself with our step-by-step guide below.

Why Is It Important?

Every set of 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.

optical center which is determined by pupillary distance.

Optical Center

Necessary Tools

Your prescription may tell your PD. But if the PD is not available, use your friend or a mirror to help you figure it out.

Pupil distance measuring ruler

Millimeter Ruler



Print PD Ruler

1. Print PD ruler at 100% size. Do not use ‘scaling’ or ‘fit’ setting. Print setting should be ‘actual size’.

Print pupillary distance ruler

Fold the Ruler

2.Fold printout along the dotted line.


Steps To Measure Your PD


Position yourself arm’s length from your friend or yourself approximately 8 inches (20cm) away from a mirror.

Measure pupillary distance Step1


With your face straight, hold the ruler against your brow.

Measure pupillary distance Step2


Close your right eye and align the 0 mm over the center of your left pupil.

Measure pupillary distance Step3


Close your left eye and note the reading directly over your right pupil. That will be your Total PD.

Measure pupillary distance Step4


You also need to measure the distance from two pupils to the center of your nose respectively to make sure that if you have two PDs (OD & OS).

Measure pupillary distance Step 5

A Few Things to Note

Measure your PD 3-4 times to ensure it’s accurate and consistent.
Range of Adult PD: 54-74 mm
Range of Child PD: 43-58 mm

Having a Friend Measure Your PD

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.

1.Look straight ahead with both eyes.
2.Keep your eyes as still as possible.
3.Do not look at the person measuring!
4.Repeat the measurement to ensure accuracy.

Friend Measure Your Pupillary Distance

What Is Single Vs Dual PD?

SINGLE 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 Pupillary Distance


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: 30/30. The first number is always the right eye (OD) measurement, and the second number is the left eye (OS).

Single Pupillary Distance



How Do You Calculate Near PD For Reading Glasses?

You can calculate Near PD for reading glasses by subtracting 3mm from your distance PD. For example, if your distance PD is 63mm, then your near PD is 60mm.

If you are using Dual PD to calculate near PD, then subtract 1.5mm from each eye’s measurement. For example, if your dual PD is 33/31mm then your near PD would be 31.5/29.5mm.

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