How to Measure Pupillary Distance: An In-Depth Guide


Measuring your pupillary distance (PD) is one essential step to ensure that your glasses fit perfectly and protect your eyesight. This optical measurement, defined as the distance between your pupils’ centers, is vital to ensure the proper alignment of the lenses with your eyes. It may also be used for other medical reasons like detecting a vision disorder or prescribing corrective eyewear. In this comprehensive guide, we will take you through everything you need to know about measuring your pupillary distance.

Step-by-Step Guide

While measuring your PD may sound daunting, it is relatively easy and comfortable to do so from home. Here are the steps for measuring your PD using a ruler:

  1. Stand in front of a mirror and place a millimeter ruler on the bridge of your nose.
  2. Close one eye, and align the ruler’s zero with the center of your pupil.
  3. While keeping the ruler steady, close the other eye and open the previously closed eye.
  4. Read the measurement from the ruler that aligns with the center of the other pupil.
  5. Repeat the same process a few times to obtain an average PD measurement.

If you don’t have a millimeter ruler, you can print out a PD ruler and use it for measurement. It should be available on your eye doctor’s website or simply search for it online.

Another way to measure your PD is by using a mirror and a ruler:

  1. Place a ruler horizontally in front of your eyes and look straight ahead into the mirror.
  2. While keeping your head still, place a ruler against your browline, with the ‘0’ line over the center of one pupil.
  3. Close the eye you started with and open the other one; the ruler should still align with the center of your first pupil.
  4. Read the measurement from the ruler that aligns with the center of the second pupil.
  5. Repeat the process several times to obtain an average measurement.

Make sure always to take several measurements to increase your precision and minimize errors and write them all down.

Tips for Ensuring Accuracy

  • Avoid tilting your head during the measurement process.
  • Always stand comfortably straight with your eyes leveled, and feet shoulder-width apart.
  • Do not take measurements after working on the computer for an extended period or when experiencing eye strain.
  • If you use eyeglasses, take measurements without them, and ask someone to help you if needed.
  • Ensure you are standing in a room with ample natural light and no shadows.

Video Tutorial

Measuring pupillary distance has never been easier thanks to instructional video tutorials. Unlike written instructions, video tutorials provide visual guidance, simplifying the process and eliminating the possibility of misunderstanding.

Here’s a helpful video that walks you through the pupillary distance measuring process step by step:

Tips for Ensuring Accuracy

  • Ensure that you have uninterrupted internet access during the tutorial.
  • Follow each step as closely as you can and pause the video when required.
  • Eliminate any distractions, like background noise or other visual stimuli.
  • Make sure your room is well lit.

Text + Illustrations

Pairing text with illustrations is one of the best ways to simplify the process and make it easier for you to understand. Here are some detailed illustrations for measuring your pupillary distance:

Illustration of Measuring Pupillary Distance

Tips for Ensuring Accuracy

  • Be sure to follow each illustrated step precisely.
  • Check what you have drawn or written with the illustrated steps from time to time.
  • Choose a guide with legible writing and clear images, and go through it multiple times so that you grasp the process and commit it to memory.

Comparison of Different Methods

While there are different techniques to measure pupillary distance, the two methods discussed above are the most common. These two techniques have some pros and cons that you might want to consider:

Using a Ruler:

  • Pros: It’s the most reliable method, and you can do it yourself without any help.
  • Cons: It is challenging to keep the ruler steady or aligned throughout the process, making it prone to error.

Using a Mirror and a Ruler:

  • Pros: You don’t need another person’s help, you can perform it comfortably and, compared to using a ruler, it’s easier to keep steady.
  • Cons: It may be a bit more challenging at first, as orientation might be difficult, and the measurement may not be very accurate sometimes.

Choose a method that appeals to you based on your available equipment and preference.

Tips for Ensuring Accuracy

  • Master one technique before trying another.
  • Perform multiple measurements to mitigate errors.
  • Write down every measurement you take, as it may serve as a reference in the future.

Equipment Guide

Note that all you need is a millimeter ruler, preferably made of metal or a PD ruler. However, here’s a list of what you need:

  • PD Ruler: A specialized ruler that helps measure your PD accurately, designed to rest on the bridge of the nose and provides very precise markings for the measurement.
  • Millimeter Ruler: A simple ruler with millimeter markings.
  • Smartphone App: Certain apps use your phone’s camera to measure PD.
  • Printable Ruler: You can download and print such rulers online and cut out the printed template for measuring purposes.

Here are the recommended equipment options based on their prices:

  • Budget Option: Printable Ruler ($0-5)
  • Mid-Range Option: Millimeter Ruler ($6-15)
  • Premium Option: PD Ruler ($30-50)
  • App Option: Some apps are free, while others cost $3-5 to download.

Tips for Choosing the Right Equipment

  • Consider your budget and current equipment. If you have a millimeter ruler or phone app, you may not need to make any further purchases.
  • If using a printable ruler, ensure that the printer settings are correct and the paper is of high quality.
  • If buying a PD ruler, make sure it’s made of durable materials and comes with a protective case.
  • Try out different equipment before sticking to one option to find what works best for you.

Expert Advice

While measuring PD is relatively simple, it helps to get expert advice from a qualified professional. We spoke to an eye specialist to provide you with some practical tips and advice.

Interview with an Optometrist

Q: How important is it to measure one’s PD?

A: It’s crucial to measure PD accurately since it determines how you look through your new glasses. If your lenses don’t align properly with your eyes, you may experience double vision, eyestrain, headaches, or experience difficulty focusing.

Q: Can measuring your PD at home be trusted?

A: Yes, you can measure your PD at home and most people prefer it that way, but you have to ensure you’re taking accurate measurements. Both methods discussed here work best, and you need to have a steady hand while performing the measurement.

Q: Are there any extra tips you would suggest?

A: Yes, one complete measurement set should contain three readings. Using a partner can help you to get more accurate results. One should face the wall while measuring in front of a mirror. And finally, make sure that the tool being used is clean or sterilized before use.


Measuring your pupillary distance may seem complicated, but this guide has provided you with all the information and resources you need to do it comfortably at home. Whether you prefer the step-by-step guide, the video tutorial, or the detailed text with illustrations, all you need to do is find the method that works best for you.

Remember always to perform multiple measurements to increase your accuracy, invest in appropriate equipment, and seek expert advice when needed.

So, go ahead and start your measurement startup, try it out, it’s efficient and may not take longer than a couple of minutes.

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