Pupillary Distance: How to Measure It

Measuring Pupillary Distance: A Step-by-Step Guide

What is single vs. dual pupillary distance?

Single 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. Read below to learn how to calculate near PD for reading glasses.

Dual PD

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).

How to measure pupillary distance

You can ask your eye doctor to include your PD measurement on your prescription. You can also use one of the following methods to measure your own pupillary distance.

By yourself
You will need a mirror, something to note information down, and a ruler marked in millimeters.

1. Position yourself

Position yourself approximately 8 inches (30 cm) away from a mirror.

2. Look in the mirror

Look straight ahead into the mirror and position the ruler over the bridge of your nose.

^{Do you already own a pair of glasses?}

^{Wear them during this step.}

3. Measure

Close your left eye and align the 0 mm over the center of your right pupil. Measure the distance from center of your right pupil to the center of your nose. Repeat with the left eye.

^{If you are wearing your glasses you can use a marker to draw the point directly there}

4. Write it down

If the PD value is the same for both eyes you can sum them and obtain a single value (this means you have a single PD), otherwise mark both values (this means you have a dual PD and you will have to insert both values).

With the help of a friend

You will need a friend to measure and a ruler marked in millimeters.

1. Face your friend

Make sure your friend is standing in front of you, at a 40 - 50 cm distance (should be the length of your friend’s arm stretched out)

2. Center your ruler

Have your friend align the ruler over the bridge of your nose. The 0 mm should be over the center of your right pupil.

^{Do you already own a pair of glasses?}

^{Wear them during this step.}

3. Measure

Focus into your friend’s right eye. Ask them to measure the distance from center of your left pupil to the center of your nose. Repeat the process with the other eye.

^{If you are wearing your glasses}^{you can use a marker to draw the point directly there}

4. Write it down

If the PD value is the same for both eyes you can sum them and obtain a single value (this means you have a single PD), otherwise ask your friend to mark both values (this means you have a dual PD and you will have to insert both values).

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