How to Measure Pupil Distance ？

March 31, 2023     Sherry

Interpupillary distance refers to the distance between the centers of the pupils of the two eyes, in millimeters, and is an important parameter when dispensing glasses.
If the interpupillary distance measurement is inaccurate, it will affect the visual effect and comfort of the glasses, and even cause eye fatigue, dizziness and other problems. Therefore, measuring your pupillary distance correctly is a necessary step for dispensing glasses online or in-store.

So, how do you measure your pupillary distance? This article will introduce two commonly used measurement methods: one is to use a professional interpupillary distance ruler or ruler; the other is to use devices such as mobile phones or computers.

Method 1: Use a Professional Pupil Distance Ruler or Ruler

This method requires another person to help with the measurement, and the steps are as follows:

The examiner and the examinee are about 40 cm apart and face to face, so that the eyes of the two are kept at the same height. The examiner holds the pupillary ruler or ruler with the thumb and index finger of the right hand, rests fingers against the cheek of the examinee, and then places the pupillary ruler at the lowest point of the bridge of the nose, and tilts slightly along the angle of the bridge of the nose. The examiner asked the examinee to close the left eye first, then observe the scale corresponding to the pupil center of the right eye, and write down the value.
The examiner asked the examinee to close the right eye again, then observe the scale corresponding to the pupil center of the left eye, and write down the value.
Add the two values to get the total interpupillary distance of the person being checked.

Method 2: Use mobile phone or computer and other devices

This method can be measured by yourself, the operation steps are as follows:
Take a ruler or tape measure and place it on your forehead, near your eyes.
Take a photo of yourself with your mobile phone, pay attention to extending your arms to about 60-70 cm, and look straight ahead with your eyes. Import the photo into the computer or mobile phone, and use a drawing tool or other software to draw two points on the photo, corresponding to the centers of the pupils of the two eyes.
Use a paint tool or other software to measure the distance (in pixels) between the two points and write down the value.
Use the formula to calculate your total pupillary distance: total pixels/pixel ratio = total millimeters. The pixel ratio refers to how many millimeters each pixel represents, which may vary on different devices45.
The above is about how to measure yourself and how to measure the interpupillary distance

The two measurement methods of the pupil distance, hope to help you. When measuring the interpupillary distance, you need to pay attention to the following points:
Be natural and relaxed when measuring, don't squint or widen your eyes.
When measuring, keep your head facing the camera or the examiner, and don't tilt your head or face sideways.
When measuring, avoid too strong or too dark light, so as not to affect the pupil size and clarity.
Be as accurate and careful as possible when measuring, and it is best to take the average value of multiple measurements.
If you already know your pupil distance, then you can choose the right glasses online or in store according to your needs and preferences. When choosing glasses, in addition to considering the interpupillary distance, other factors should also be considered, such as face shape, nose bridge, ears, color, material, etc. If you're not sure what style of glasses is right for you, you can consult a professional optician or use some online fitting tools.

In short, measuring the interpupillary distance is the first step in dispensing glasses, and it is also a very important step. Only by correctly measuring your own interpupillary distance can you ensure the visual effect and comfort of the glasses. Hopefully this article has given you a better understanding of how to measure your own IPD and given you some pointers for choosing the right glasses. However, it is still recommended that you go to a regular and professional optical shop or eye hospital for measurement, which is also a kind of protection for yourself.