Eyeglasses | SmartBuyGlasses Hong Kong

How to Measure Pupillary Distance

What is Pupillary Distance?

Pupillary Distance (PD) is the distance between the pupils of your right and left eye. Measuring pupillary distance is typically done by your glasses providers, as it is used to fit your glasses to your eyes. The distance between the optical centers of your eyewear lenses should be the same as your interocular distance for proper vision correction. Your optician should provide your pupillary distance after an eye exam.

However, in case it isn’t given to you, our following guide will show you how to find pupillary distance. When measuring pupillary distance, you can either do it by yourself with a mirror or ask a friend for assistance to get an accurate measurement of your pupillary distance.


How to Find Pupillary Distance with Assistance  

Step 1 – Your pupillary distance ruler can be any millimetre ruler. Hold the pupillary distance ruler up to the bridge of your nose.

Step 2 – Have a friend stand about an arm’s length away from you, or face a mirror.

Step 3 – Close your right eye and ensure the pupillary distance ruler’s zero is aligned with your left pupil looking in the mirror or asking a friend. 

Step 4 – Keeping the pupillary distance ruler still and look straight ahead, close your left eye and open your right eye.

Step 5 – Read (or have your friend read to you)  the number that aligned with the center of your right pupil. This number is your pupillary distance.

Step 6 – Repeat the process to ensure the most accurate result.​​​


There are a few tips that you can take when a friend is measuring pupillary distance:

• 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.

What is the Average Pupillary Distance?

The average pupillary distance for most adults lies between 55 and 65mm, while the average pupillary distance for children is usually between 42 and 54mm. However, for some people pupillary distance can vary outside these typical measurements.


Once you’ve got your pupillary distance, you can check out our range of Prescription Glasses and Prescription Sunglasses.